rate 



CIRCULAR 

—4—OF—8— 

]\Jalter, Jmp & Rogers 

ENGINEERS AND CONTRACTORS 


San Francisco, Cal 


§FCf*7?? 




































































































Notice 


Special 


We make contracts to furnish and completely erect at the mines, in the United 
States, Mexico, and other foreign countries, Reduction Works of all descriptions for the treatment 
of gold, silver, copper or lead ores. 

Among the many works we have constructed are the following: 


Name. 

Mill. 

Stamps. 

Location. 

Standard. 


20 

.Bodie, Cal. 

Noonday. 

.Silver. 

. 30 

Bodie. Cal. 

Bodie Tunnel. 

. jf. Silver. 

. 20 

.Bodie, Cal. 

Homestake. 

.Gold.. 

. 120 

. Black Hills, Dakota. 

Plymouth. 

.Gold.. 

. 40 

.Plymouth, Cal. 

Valentine. 

.Gold.. 

.. 20 

.Amador Co., Cal. 

Rainbow. 

.Gold.. 

10 

.Sierra Co., Cal. 

Contention ..... 


. 25 

.Tombstone, A. T. 

Grand Central. 


. 30 

.Tombstone, A. T. 

Girard..•. 


. 20 . 

.Tombstone, A. T. 

Head Center. 


10 

.Tombstone, A. T. 

Bradshaw .. .. 


10 . 

.Tombstone, A. T. 

Silver Cliff. 


40 

. Colorado. 

Game Ridge. 


. 40 

.Colorado. 


Name. 

Mill. 

Stamps. 

Location. 

Palmetto. 

Silver. 

. 15 

. Colorado. 

Mimbres. 

Silver. 

10 

.New Mexico. 

Carlisle. 


. 20 

.New Mexico. 

Elkhorn. 

Silver. 

10 . 

. Montana. 

Gregory.^Concentration 

Works. 

.200 tons. 

. Montana. 

St. Helena. 

Silver. 

. 60 . 

.Sonora, Mexico. 

Tiger. 


10 . 

. Arizona. 

Sheep Ranch . 

Gold... 

. 20 . 

. California. 

Reilly. 

Silver.. 

10 . 

. California. 

Silver Queen (Lim.) Concentration Works. 

150 tons. 

.Sonora, Mexico. 

Falcon. 

Silver. . 

. 20 . 

. Nevada. 

Alexander. 

Silver.. 

. 40 . 

. Nevada. 

La Trinidad (Lim.) Concentration 

Works. 

300 tons. 

.Sonora, Mexico. 

Florence . 

Silver. . 

. 20 . 

.Dakota. 


Copyrighted, 1887, by MALTER, LIND & ROGERS. 



































OF 








































T RM1 









PREFACE. 


We have been engaged for many years in the business of building, furnishing and erecting all 
descriptions of Mining Machinery in nearly every mineral section of the United States and Mexico. 
We are thoroughly conversant with the mechanical and metallurgical work of reducing Gold, Silver, 
Copper and Lead Ores, having learned try widely extended practical operations much that is necessary 
to insure the best results in the treatment and handling of all classes of free and rebellious Ores— 
which information could not be acquired except by actual contact with the difficulties met in their 
profitable reduction under many varying conditions. 

This experience will be found to be of great value to our customers in aiding them to guard 
against wasteful experiments, and in assisting them to obtain the most effective works, at the least 
possible cost. 

We assure our patrons of the most thorough, consientious and reliable performance of all work 
intrusted to us. Respectfully, 

MALTER, LIND & ROGERS. 








Metallurgical Tests. 


The importance of Laboratory Work to the practical 
Metallurgist is generally under-estimated, for the reason that 
scientific attainments and practical experience rarely go 
hand in hand. The chemist can only make his knowledge 
available by combining it with the practical experience of 
the metallurgist, and the fact that this has frequently been 
overlooked, has tended to bring Laboratory Work in exper¬ 
imental Metallurgy, in disrepute. 

The first step in all Metallurgical Work is to ascertain the 
constituents of the ore to be treated and the character of 
their combination In some cases a simple assay is suffi¬ 
cient, but in many others'a careful analysis is necessary to 
determine, at least approximately, by what methods the ore 
can be worked to best advantage— 

Then should follow working tests, which the analysis 
indicates as appropriate, in order to ascertain the best con¬ 
ditions ruling the case in question. Analysis of the prod¬ 
ucts and by-products obtained must be made, and metallurg¬ 
ical experiments, modifying and changing ordinary processes, 
are frequently rendered necessary by abnormal conditions. 

When, after proper investigation, a mode of working is 
decided upon and the necessary plant has been procured, 
the work of the laboratory does not cease. Aside from the 
assays and examinations, which are constantly made in order 
to control the work done, more intricate investigations are 
often necessary to find the causes of difficulties presenting 
themselves, and their proper remedies. 

If all work of such character were to be done on a large 
scale, the cost of it would be enormous, and the losses in ex¬ 
perimenting very great. Still this has frequently been done, 
and many enterprises have failed in consequence of it. A 
hypothetical case will illustrate these facts more clearly, 
for example : 

An ore containing Silver, Copper and Lead, by careful 
analysis, proves to contain these metals in combination with 
sulphur only, with a gangue of silica alumina, lime and 


oxides of iron. The proportions of its constituents indi¬ 
cate that the ore could not be profitably roasted and amal¬ 
gamated or smelted. Concentrating tests prove that the ore 
may be greatly enriched by concentration, with but little 
loss and at slight cost. 

Smelting tests of the concentrations prove that a Copper 
Matte, containing all the Silver, is easily obtainable, and 
these methods, being the most suitable for the reduction of 
the ore, are accordingly adopted. 

All such information can be obtained at a trifling expense, 
by forwarding a fair average sample of the ore to us, while 
to carry out any one of the operations mentioned on a large 
scale would entail great expenditures. 

Work of such character can be done thoroughly and 
reliably at the Laboratory, by metallurgical chemists of 
long and extensive experience only, who take into account 
all conditions under which practical operations on a large 
scale must be conducted. 

We examine mines and metallurgical works, investigate 
ores, and give directions for their treatment. If we are 
intrusted with the preliminary examination of ores, we will 
have them analyzed and tested by practical working pro¬ 
cesses, giving customers the benefit of our wide range of 
experience in determining the most advantageous method of 
reduction. 

For preliminary investigation only a few pounds (average 
sample) of the ore need be forwarded to us, after which we 
will be able to fix the quantity needed for a complete exam¬ 
ination and working tests. To our patrons we will give 
full directions for the proper sampling of the ores, concen¬ 
trations or tailings to secure a fair average. If we are con- 
suited in regard to the method by which ore is to be reduced, 
and the construction and erection of works intrusted to us, 
we will guarantee successful results. 

We are prepared to give a liberal credit to our patrons, 
upon fair security. 






5E^tioiMi eLeVatioN 

OF 

GOLD MILL. 

BUilf I3Y 

MALTER, LIND ^ ROGERS. 

5aN fKAriC^C°-C A ^ °5-' A ' 


Fix ATE 1, 

























































































































CIRCULAR OF MALT 


STAMP MILLS FOR THE TREATMENT 
OF GOLD QUARTZ. 


The requisites for good stamp mill machinery are strength, 
simplicity of construction, and patterns that will give the 
highest percentage of crushing and amalgamating capacity 
with the least expenditure of labor and power. 

When such machinery has been obtained and placed under 
the control of intelligent labor, the best results can be ex¬ 
pected in the treatment of either gold or silver bearing ores. 

Many contrivances have been invented for the purpose of 
dispensing with the use of stamps in the reduction of ores, 
but up to the present date nothing has been found to equal 
them for general and practical every-day work. 

Plate No. 1 shows the simplest plan of stamp mill for 
treating free gold quartz. 

The power is furnished by a hurdy gurdy water-wheel, 
secured to a horizontal shaft, the power from which 
is transmitted directly by means of pulleys, rubber belts, or 
hemp or wire rope to the line shaft of the battery. 

This mill contains neither rock-breaker nor automatic ore- 
feeders, and is designed to meet the wants of those whose 
means are limited, and who, preforce, must use economy in 
the first outlay. It is, however, so arranged that rock- 
breaker, ore-bins and feeders can be added at any future 
date, as shown by the dotted lines, without disturbing the 
balance of the plant already in place. 

This mill being designed for treating only free milling- 
gold ore, is of the simplest possible construction. The gold 
is liberated from the quartz or gangue by crushing under 
stamps, and at once amalgamated with the quicksilver in the 
mortar, without further treatment, the amalgam thus formed 
being held in the mortar and upon copper sluice-plates out¬ 
side the mortars until the usual clean-up takes place. 


. LIND & ROGERS 


o 


Plate 2 shows a more complete plan of modern stamp 
mills for the treatment of free gold quartz, containing no 
valuable sulplmrets and hence requiring no concentrating- 
appliances. It illustrates the essential features of the mills 
which we have constructed for the mines in the Black Hills, 
Dakota Territory and in California. 

This plant contains ore screens, rock breakers, ore bins and 
automatic feeders and all other necessary appliances for bat¬ 
tery reduction and amalgamation ; the motive power being- 
obtained by means of a high pressure water-wheel. 

The framework of this mill is constructed with special 
view to give it strength and durability. The mill contains 
all convenient appliances for cheaply handling the ores and 
operating the works. 

Plate No. 8 shows another and similar design of stamp 
mill, with concentrators. 

This mill is designed to treat ores containing gold bearing 
sulplmrets, of the character most commonly found in Cali¬ 
fornia. It has all of the useful appliances for a first-class 
plant of this kind, including ore screens, rock breakers, 
automatic feeders, batteries, copper-plated sluices and con¬ 
centrators, using either steam or water as the motive power. 

In the separation of gold bearing sulphurets from the 
tailings of stamp mills, it is not generally thought necessary 
to size the ores for concentration, and, therefore, the process 
in use is quite simple, the machines employed being usually 
of the endless belt or shaking table patterns, shown in the 





(i 


CIRCULAR OF MALTER, LIND & ROGERS. 


Plate No. 4 illustrates a stamp mill with pan amalgam¬ 
ation suitable for gold ores, from which the precious metals 
cannot be extracted by the ordinary mortar amalgamation, 
for the reason that it does not permit of heating the mercury 
and water used. Only the purest gold can be dissolved in 
cold mercury; gold containing traces of silver or other 
metals, will not readily amalgamate in cold mercury. For 
this reason, battery amalgamation is at best an inefficient 
process in many cases, causing much loss of valuable metal, 
particularly in the working of clayey ores, in which, the 
gold is finely divided and not altogether free as is usually 
the case. 

Battery amalgamation is successful only in working clean 
quartz ores, containing pure and coarse gold, the finer gold 
is easily carried away from the mortars and copper plates 
by the currents of water, and low grade gold will not adhere 
to the amalgamated copper plates. 

Many financial failures have resulted in working valuable 
mines for the reason that battery amalgamation has been 
attempted upon ores which should have been subjected to 
the more effective treatment in pans. 

The ores from many mines which are being worked in a 
measure successfully, do not yield more than 50 or 60 per 
cent of the valuable metal by the battery process of amal¬ 
gamation. With but few exceptions, much more satisfactory 
results could be obtained by subjecting gold ores to a pan 
amalgamation process similar in manner to that in which 
silver ores are treated. 

The first cost of such a plant is somewhat greater than 
that of the ordinary gold mills, but the increased percentage 
of reduction per stamp and actual saving in precious metal 
which can be effected, will soon repay any additional outlay 
in first cost. 


Plate No. 5 shows a mill for the reduction of gold ores of 
a more complex nature. The gold, which although free 
from union with refractory metals, being in alloy with 
some silver, will not readily amalgamate with cold mercury 
hence requires pan amalgamation, differing, however, in the 
construction of pans used. 

The sulphurets being valuable and of such a nature as to 
resist and interfere with the amalgamation of the gold in 

o O 

pans requires previous separation by means of concentrating 
machines. 

The ores are brought from the mines to mill by means of 
wire rope tramways. 

In this mill, the battery serves solely for the purpose of 
crushing the ores; the amalgamation is altogether effected 
in the pans, after the gold bearing sulphurets have been 
separated by means of the concentrating machines placed 
between the battery and pans. The settlers in this plant 
operate the same as in silver mills to settle and separate the 
amalgam from the pan tailings. 

Plate No. 6 shows ground plan of the mill shown in plate 5. 

Design No. 7 illustrates the general character of continu¬ 
ous working gold mills, using our patent grinding mill in 
connection with the battery. 

Ore can be more cheaply reduced to a certain degree of 
fineness in a stamp battery than by any other means, but 
after having reached that degree of fineness, it is more easily 
ground. The use of an arrastra largely increases the crush¬ 
ing capacity of the battery mill, especially with ores in which 
the metal is finely divided, and which, therefore, requires to 
be reduced to a very fine state to permit the extraction of 
the gold. 

The ore, after passing the crushers, is handled entirely by 
automatic machines. 






5EiqHOrslAL^lbE ELEVATION 
or a 

60 STAMP 60LDPUARTZ MILL, 

WITH 

BATTERY AMALGAMATION 

built BY, MALTER, '(lINDS ROGERS. 

5*o franco, fa 
M A* 

4TH. cf-.iff &r. A ^<Y. ;>*K 



plate 2 












































































































CIRCULAR OF MALTER, LIND ROGERS. 


Plate No. 8 shows sectional side elevation of one hundred 
and twenty stamp gold mill which we furnished and built 
for the Homestake Mining Company at the Black Hills, 
Dakota Territory. 

The ore bins are placed between the batteries which are 
thus arranged back to back. 

The ore is delivered to this mill by means of narrow guage 
locomotive and cars not shown in the drawing. 

Plate No. 9 illustrates the same general character of mill 
the ore bin floors are Hat instead of being placed at an 
incline as shown in plate 8. 



8 


CIRCULAR OF MALT! 


SILVER MILLS. 


Silver mills may be classed under two heads : 

Ut. -Tbe wet crushing and raw amalgamating mills. 

-'!• I he dry crushing and chloridizing mills. 

The first structures are less complicated, less costly, and 
by them the ores can be treated more cheaply than by 
dry crushing and roasting, but are of service only in work¬ 
ing those free ores which contain the precious metals in the 
form of chlorides. 

In the second class of mills, ores containing silver in any 
state may be worked, provided there be not too much base 
metal in connection with the silver. 

WET CRUSHING MILLS. 

Ill wet crushing mills, the pulp is deposited either in 
wooden settling tanks, shown on plans, or directly in grind- 
ing pans as in the continuous process elsewhere described. 

In the settling tanks, the pulp carrying the metals, grad¬ 
ually sinks to tlie bottom, while the water used in the bat¬ 
tery to facilitate crushing, is partially carried away by 
means of sluices arranged for that purpose, or is pumped 
back, o lie used again in the battery for the purpose of 
economizing water, and also for the purpose of saving the 
very fine and valuable metals floating in the water. From 
the tanks, the pulp is shovelled or pumped into the grinding 
pans, where quicksilver and chemicals are added, and the 
further grinding and treatment proceeded with; in this 
process, the friction of iron surfaces, in contact, are strong 
agents in the decomposition of the sulphurets of silver. 

Many combinations of chemicals depending upon the 
character of the ores under treatment, have been used— 
some useful and others useless; among the most common are 
salt, sulphate of copper (blue vitriol), sulphuric acid and 
sulphate of iron—also cyanide of potassium, etc. 


R, LIND A ROGERS. 


Wet crushing silver mills, may again be classed under 
two heads : 1st.—Those which ivoi‘k in charges, and 2d, 
those which ivork continuously. 

Design No. 10 shows one of our plans for the construction 
of a wet crushing silver mill of the first description, as 
most commonly used in it, all of the convenient accessories 
are provided to save labor as much as possible. 

The ores are first introduced into the mill in the ore- 
house, shown at the top of the drawing—to the left— 
dumped over ore-screens, made of iron bars, into the receiv¬ 
ing ore-bins beneath, while the coarser passes on to the rock- 
breaker floor, where it is crushed finer, by crushers provided 
for that purpose, and then also falls into the bins beneath, 
from which it is conducted by chutes to the automatic 
ore feeders which supply the stamps as required. 

Each mortar has sheet iron or wire screens, more or less 
fine, through which the crushed pulp escapes and is then 
conducted to the settling tanks or pans as the case may be, 
where the grinding and amalgamation is completed; from the 
pans, the pulp is discharged into the settlers and thinned by 
the addition of water to settle the amalgam, which is then 
drawn off to be retorted and melted into bars for shipment. 

dhe time required for reducing a given quantity of ore, 
depends largely upon the design of the crushers, mortars 
and pans, as also upon the character of ore under treatment. 
In the continuous plan, the pulp charged into one or more 
pans, makes a continuous circuit of several pans and set¬ 
tlers, before it is drawn off; should the amalgamation begin 
in one pan, and not finish there, it continues in the next and 
so on until it is completed. these mills are especially 
adapted for low grade ores, in which all possible expense of 
handling must be avoided. 



CIRCULAR OF MALTER, LIND & ROGERS. 


Plate No. 11 shows the ground plan of a twenty stamp con¬ 
tinuous working silver mill, with Lind battery frames. In 
this plan, only six of our patent pans and two settlers are re¬ 
quired for twenty stamps. The pulp from the settlers is 
sized by means of the hydraulic separators, before it is con¬ 
centrated upon the tables. 

Silver ores, unlike gold-bearing pyrites, are not so readily 
concentrated, and require to be sized before treatment on 
tables, as the specific gravity of silver ores is not so great as 
that of gold ores. 

Design No. 12 illustrates a continuous working wet crush¬ 
ing silver mill for soft and decomposed ores, in which plan, 
the battery is replaced by our patent arrastra grinding mill. 

The ore is prepared for the arrastras by means of coarse 
and fine crushers, as shown in the design. 


9 

DRY CRUSHING AND ROASTING SILVER MILLS. 


In the process of treating the so-called rebellious silver 
ores, containing sulphur, antimony, arsenic, lead, copper, 
etc., in combination, a chloridizing roasting, with salt, is first 
employed, before amalgamation can be successfully accom¬ 
plished in pans. 

In this process, the ore coming from the mine is first 
dried by heat, either on platform or in mechanical dryers else¬ 
where described, before being introduced into the stamp 
battery. After drying, the ore is discharged into bins or ore 
feeders, from which it is fed to the stamps, crushed dry un¬ 
til sufficiently pulverized to be discharged through fine wire 
screens into conveyors which carry it to the elevators; they 
in turn elevate it to the bins located near the roasting fur- 
naces, from which it is fed into furnaces where the roasting 
is effected. 

T1 ie salt is sometimes crushed in the batteries with the 
ores, but more frequently in separate crushers or batteries, 
for the reason that salt is a substance which easily absorbs 
moisture, forming a paste with the ore which is apt to clog 
the screens. The proper percentage of salt is fed with the 
pulverized ore into the roasting furnace, after the roasting 
process is completed; the pulp is discharged on cooling floors 
and from there transported to the pans in cars provided for 
that purpose. 

The after treatment in the.pans, is similar to that used in 
the wet process, only that little or no grinding is done. 

In this process, the roasting is a very important feature, 
and upon it depends largely the after success in amalgama¬ 
tion. 




10 


CIRCULAR OF MALTER, L1N1) & ROGERS. 


There are several patent furnaces in successful use: the 
Stedefelt, Bruckner, White, White & Howell, Dodge and 
O’Harra, all are useful under different conditions. 

Where the ores are to be roasted in charges, the Bruck¬ 
ner furnaces are generally used, but the White, Dodge or 
Stedefelt patents are preferable where the ores do not require 
long continued roasting. 

Design No. 13 shows the side elevath n of a 20-stamp 
dry crushing and roasting silver mill, having rock-breaker, 
revolving dryer, ore feeders, batteries, conveyors, revolving 
roasting furnaces, pans and settlers, with the latest improve¬ 
ments in all details affecting the working of the mill. 

Design No. 14 shows ground plan of a similar mill. 

IMPROVEMENT IN DRY CRUSHING. 

Dry crushing batteries, as usually constructed, do not give 
more than 00 per cent of the work done by a wet crushing 
battery. 

The crushing capacity of the battery can be greatly in¬ 
creased however, by using our patent re-screening device 
in which two sets of screens are used. The first screens 
somewhat coarser than the ore required for subsequent 
working are placed in the sides of mortar and the second 
screens just fine enough for the ore are placed outside of the 
mortar beneath and directly in front of the others. By this 
arrangement the crushed ore is more readily discharged 
from the mortar and the stamps do not expend useless force 
in continuing to hammer upon it after being sufficiently 
fine. Unnecessary pounding and shining of the ore is 
thereby avoided, the crushing capacity of the stamps largely 
increased and the loss from float dust and sluice are greatly 
diminished in the subsequent working it before it is dis¬ 
charged through the screens. The great importance of this 
can only be appreciated by mill men who have had experi¬ 
ence in working ores by the dry process. 


Cuts No. 1-2 show a sectional view of dry crushing battery 
fitted with our patent rescreening device, in which (C) is a 
stamp working in the cast iron mortar (B). (A) represents 

the battery screens, which in this arrangement are much 
coarser than those usually employed for dry crushing. (D) 
is a fine screen set at an angle with the mortar; upon it 
the powdered ore falls as it comes through the screens (A) 
That which is fine enough then passes through the screen (D) 
to conveyors (F) which take it to the elevator feeding the 
roasting furnaces; that which is too coarse to pass the 
screen (D) passes over it to the elevator (E) and by it is 
returned to the mortar to be recrushed. 






11 


CIRCULAR OF MALTER, LIND & ROGERS. 




Cut 2.—Standard patent rescreening- Battery for 
Dry Crushing- Stamps. 


Cut 1. 














































































































































































12 


CIRCULAR OF MATTER, LIND A ROGERS. 


STAMP BATTERY. 


A stamp battery consists of the following parts : 

Mortar, cam-shaft, driving pulley, cams, bearing boxes, 
stems, stem shoe and die, stamp heads, tappets, guides and 
the battery frame. 

BATTERY FRAME. 

The battery frame is usually built of heavy timber ; iron 
frames are not any longer in use, they do not well serve the 
purpose ; it is practically almost impossible to construct them 
in such a manner as to withstand the wear and tear conse¬ 
quent to the great jar of the stamp. 

The mortars are set upon heavy wooden blocks, standing 
upon end and being from twelve to sixteen feet in length. 
These so-called mortar blocks arenot rigidly attached to thebat- 
tery frame proper, which carries the shafting, in order to avoid 
the transmission of the jar of the stamp to the machinery. 

Battery frames are not generally made to receive more than 
10 stamps. In large mills, a number of separate frames, each 
carrying 10 stamps are placed side by side. Ordinarilly, each 
frame for 10 stamps has three posts with the necessary sills 
and braces. In mills having 20 stamps or more, two 10 stamp 
batteries are sometimes connected so as to make one post 
support the ends of both cam-shafts. This center post is then 
made of heavier timber. A battery so constructed is shown 
on plate 5 the driving pulley is secured to the end of the 
cam-shaft and overhangs its bearing. 

The accompanying plate shows a front elevation of a 
10 stamp battery frame, of our improved construction, 
having four posts—the driving pulley is keyed to center 
of cam-shaft—a bearing box is placed on each side of it. 





























































































































































































PLATE 3. 



^i'Ll eleV/\tioH 

or 

TWENTY STAMP GDLD MILiLt 

'with 

FRUE EONEENTRATC1RS. 

vJ i Lr £y 

MALTER, Lil ND & ROGERS. 
3an Pal- 

u-3a 

yfH, 3RiiTo(J«: ifcY, J.f. 




















































































































































CIRCULAR OF MALTER, LIN’D & ROGERS. 


13 


MORTARS. 


The mortar is the most important part of a battery. Upon 
its proper construction depends very largely the efficiency 
of the battery in its crushing capacity or as an amalgamating 
apparatus if so used, as is frequently done in gold mills. 
If the screens are given too much or too little inclination, 
the crushed ore either does not readily sieve through them, or 
it lodges upon them ; if they are set too high or too low, they 
either permit too much ore to lie upon the die, retarding 
the efficiency of the stamp, or they are exposed to too fre¬ 
quent breakage, by large lumps of ore being violently 
thrown against them by the fall of the stamp. 

For light ores, the screens must be set nearer upright, 
for heavy ores they should be more inclined. 

The less favorable the positions of the screens, the 
more of the ore is hammered into an impalpable dust, 
which often causes loss in subsequent operations by 
floating off as in roasting or amalgamating. 

It has become the almost unexceptional practice to 
make mortars to receive live stamps 

Cuts 4 and 5 show sectional views of two ordinary double 
discharge mortars, as used for dry crushing stamps. The 
bottom of mortar is from G to 7 inches thick. 

The dies are secured in their places by means of taper 
projections. 

The principal difference between these mortars is the 
degree of inclination at which their screens are set. 



Cut 4. 



Cut 5. 


Mortar for 
Dry Crushing. 


Mortar for 
Dry Crushing. 




















































14 


CIRCULAR OF MALTER, LIND & ROGERS. 


Cut 6 shows a single discharge gold mortar, as used 
in many mills in California, in which the amalgamation is 
principally effected in the mortar. A narrow strip of silver- 
plated copper is attached to the lower bar of the screen frame, 
in an inclined position, so that the “ swash ” of the ore pulp 
in passing towards and through the screen may deposit the 
gold upon it. 

The sides of the mortar are lined with a thick cast 
or wrought iron plate which may be replaced as it wears out. 

A cast iron apron, having a spout on one end, is bolted 
to the front of mortar for the purpose of carrying the dis¬ 
charged sands away into the sluices. 

The screen frame is secured in the ordinary manner by 
means of wrought iron keys. 

O 



Cut 6.—Gold Mortar. 









































ELEV^TIOH 

or 

GOLD MILL 

WITH 

GDNTINUDU5 PAN AMALGAMATION 
TAILING SEPARATORS. 

3L»itr 

MALiTER, LrIND & ROGERS. 
5aN FfVW^o, 

lirH.^^iiro^ s $-F 


PLATE <*. 


































































































































CIRCULAR OF MALTER, LIND & ROGERS. 


15 


Cut 7 shows an amalgamating gold mortar, as used 
Loth east and west of the Rocky Mountains. It differs from 
the former mortar principally in having an amalgamated 
copper plate secured to both its front and back. The front 
plate is, usually, attached to the screen frame. The back 
plate is fastened to a plank which covers an opening, 
and is secured in its place like the screen frame, by means 
of keys. In order to give these screens the most advanta¬ 
geous inclination for the purpose of amalgamation, so that 
the sands will neither lodge upon them, nor glide too rapidly 
over them, wooden wedge blocks are secured to both 
the lower bars of the screen frame and the plank in rear, 
as is shown in the cut. 

As the dies wear down in the mortar it becomes 
necessary to lower both the amalgamated copper plates 
by setting down the screen frame and the rear plank so as to 
keep uniform the distance between the lower edge of 
plate and the top of dies. 

The screen is not attached directly to the screen 
frame, so-called, which carries the amalgamating plate 
on its lower bar, but it is secured to a smaller frame, a 
screen frame proper, which is fastened to the larger 
frame by means of heavy thumb screws and check nuts. 

The arrangement makes the removal of the screen 
possible without lifting out the heavy frame and dis¬ 
turbing the copper plate. 



Mortar with Copper Plates for Crushing and Amalgamating 

Gold Ores. 












If* 


CIRCULAR OF MALTER, LIND & ROGERS. 


Cut 8 represents a double discharge wet crush- 

ini' - mortar, as used in silver mills. It has discharge 

aprons attached to both its sides. Single discharge wet 

crushing mortars are more frequently used than those having 

double discharge. 

© 

The crushing capacity of the wet crushing mortar, unlike 
the dry crushing mortar, is not very materially increased 
by giving it two discharge openings instead of one. 



Cut 8.—Double discharge Wet Crushing Mortar. 




























ELEWlO|J Of A, 

40 STAMP 60 LD Ml lib. 

WITH 

BATTERY AND PAN AMALGAMATION 

AND 

TRIUMPH CONCENTRATORS. 

JSUlLT J 31 

MAUTER, IdND & ROGERS. 

Jan f^ANCij'ro, 

QUi U-5'A: 


Plx/\TE 5 . 


U<M-r3Rl'ETorJ £, i\er, 













































































































































































































CIRCULAR OF M ALTER, LIND ,V ROGERS. 


17 



Cut 9 


Cuts 9 and 10 show a sectional mortar, designed for trans¬ 
portation on mule back, into distant mining regions to which 
no wagon roads lead. The sections are made to weigh not 
more than 300 pounds, and are planed, fitted and bolted 
with reamed bolts or riveted together. 



Cut 10.—Dry Crushing Mortar. 

Made in Sections. 


This Mortar is intended for a dry crushing battery and 
has four screen openings. The upper part of mortar is made 
of boiler plate, the bottom of cast iron. 
























































































18 


CIRCULAR OF WALTER, LIND ROGERS. 


Cut 11 shows the simplest and cheapest construction of a 
mortar, as sometimes used in distant mining regions. The 
base of mortar alone, is made of cast iron; the top is con¬ 
structed of wood and securely bolted to base and mortar 
block. Unlike the other mortars, this construction of mor¬ 
tar has a water box outside of the screen, submerging the 
screen entirely in water. The purpose of this arrangement 
is to avoid the clogging of the screen by particles of ore 
which always takes place in some degree when the water 
Hows continuously from inside of mortar toward the outside. 
If the water be held outside of the screen at the same level 
with that inside of the mortar, as shown in the above cut, a 
back splash results, which effectively clears the screen. 

This arrangement is of service when it is very desirable 
to avoid making slimes, as is usuallv the case with ores 
which are being crushed for purpose of concentration. 


Cut 11.—Sectional view of Mortar, with wooden top. 






















































«, 



Cj 

2 

< 

2 

o 


in 
oc 
□ 
i— 
d 
Dc 


et 2 

s a 

g □ 

< LJ 


2 

>-•' 

It 

LJ 

6 

00 


X 

X 

51 

=] 






















































































































































































































































































































































































































































































CIRCULAR OF MALTER, LINl) & ROGERS. 


1!) 


DETAILS OF BATTERY.—STAMP HEAD. 


H 

P 

1 

}j 


i 


Cut 12.—Stamp Head 

FOR 

Dry Crushing Battery. 



Wet Crushing Battery. 


The stamp head is secured to the stamp stem on one end 
and on the other it is made to .receive the shank of the stamp 
shoe. 

The stamp head for wet crushing batteries is sometimes 
strengthened on both ends by heavy wrought iron bands as 
shown in cut 13. 

The stamp heads are usually from 8 to 9 inches in diam¬ 
eter and from 14 to 18 inches in length, the size varying 
according to the desired weight of stamp. 


STAMP STEMS. 

Stamp stems are made of either hammered, rolled or 
calendered iron. It is from 3 to 4 inches in diameter, gener- 
erally 3|, and from 12 to 10 feet in length. Both its ends 
are turned tapering so as to receive and hold the stamp 
shoe and to permit its turning end for end. 

CAM SHAFTS. 

Cam shafts are made of hammered iron or of steel; they 
are usually from 44 to 6 inches in diameter, and should be 
provided with two keyseats placed at right angles, to serve 
in more securely fastening the cam. 

The driving pulley is secured to the cam shaft, either at 
its middle or its end, as the construction of the battery 
frame may require. 

BEARING BOXES. 

The bearing boxes of cam shafts are of a peculiar con¬ 
struction, made so as to permit their being set upon “ end 
wood ” into a cut of the battery post, and with or without 
caps. 





































































20 


CIRCULAR OF MALTER, LIND & ROGERS. 



The stamp shoe is secured by means of a taper shank 
and wooden wedges, to the lower end of the stamp head. 

Stamp shoes we make of either cast steel or of a very 
hard quality of cast iron. 

STAMP DIE. 




Cut 15.—Die for Dry Crushing Battery. 

Cut 15 shows a die for a dry crushing battery. It is cylin¬ 
drical in form, from 8 to 9 inches in diameter, and from 5 to 
7 inches in height. Two taper projections are cast on its 
lower edge at opposite sides, by means of which it is held 
in place in the mortar. It is made of hardest cast iron or 
cast steel. 


Cut 16. —Die for Wet Crushing Battery. 

Cut Hi shows a stamp die for a wet crushing battery. It 
differs from the former in having a square base which keeps 
it from turning in the mortar. 


TAPPET. 




Cut 17.—Tappet. 

Cut 17 shows two views of two and three key double 
face gib tappets. We make them of either steel or cast iron. 
















































































































































































































































CIRCULAR OF MALTER, LIND ROGERS. 


21 


CAMS. 

The cams which serve to lift the stamp are now without 
exception made with two arms. Their curve should be so 
constructed as to allow the longest possible time for the lift 
of stamp, making the lift gradual and uniform, and still 
giving the stamp sufficient time to drop. The proper curve 
of cams is an evolute. Steel cams are preferable to those 
made of cast iron, they wear much longer, but cost more. 

The lift of the stamp determines its efficiency. Seven to 
eleven inches is the usual lift. The cam should be made 
just long enough to give the desired lift; if it be made 
longer it starts the lift of the stamp by a blow against the 
tappet. 

Care must be taken not to give the cam more face than 
the tappet may cover; else the face of the cam wears 
slanting, leaving a ridge upon its outer edge which crowds 
it away from the stem and tappets and causes breakage. 

Tlie cams should be secured to the cam shaft in such a 
manner as to drop the stamps in the following order: 

One, four, two, live, three. 

No two adjoining cams must drop in turn ; else the ore 
be crowded towards one end or the other of the mortar. 

DRIVING PULLEYS. 

The pulleys which serve to turn the cam shaft are unex- 
ceptionally made of wood, fastened between heavy cast iron 
sleeve flanges to prevent their breaking in consequence of 
the jar to which they are subjected. 

GUIDES FOR STAMP STEMS. 

The guides for the stamp stems are mostly made of hard 
wood, in sets of live. A better, but more expensive way of 
making them, is of cast iron frames, so constructed as to re- 
tain separate wooden blocks for each stem. 


LOCATING MILLSITES. 


1st.—Select a site near a constant supply of good water, 
if not too far away from the producing mines. 

2d.—If possible, locate the mill on a hillside where there 
is sufficient grade or fall so that when the ore is once deliv¬ 
ered in the mill it will go through the different processes 
to the finish without requiring to be elevated. 

3d.—Avoid a location which will entail expensive grad¬ 
ing, as is found in blasting rocks or in very loose soils, 
necessitating the erection of strong retaining walls—also 
avoid sites, the lower part of which is not suitable for tailing- 
reservoirs. 









CIRCULAR OF MALTER, LIND & ROGERS. 


99 





THE STANDARD PATENT WATER HEATER AND 


PURIFIER. 


The plan of utilizing exhaust steam for heating feed water for boilers lias 
been in use for many years, and numerous contrivances have been invented 
from time to time to better accomplish this purpose. 

The nearer the boiling point to which the water can be brought before 
its introduction into the boiler,and the freer from impurities the water,the 
greater the saving in fuel in making steam, the longer the life of the boiler, 
and the easier to be kept clean. 

lo accomplish all of these results in the most thorough manner, we have 
designed and patented the standard heater and purifier, which we offer as 
superior to any heretofore in use. It can be more readily understood by 
reference to the cut. 

Hie exhaust steam from the engine is conveyed by pipes to the nozzle 
(D) and into the tee-pipe (C) which is perforated with numerous holes near 
the top to permit the passage of the steam into the body of the heater. 
At the lower end of the pipe (C), there are large openings for the admission 
of the filtered feed water to the boiler feed pipe (B). The feed water is 


supplied by means of the pipe valve and spray (H). The supply is con¬ 
trolled by means of an automatic arrangement consisting of the lever (I), 
the valve (H) and the float (J), which works in the cylinder (Iv). 

The steam rising from the pipe (C) is quickly condensed by the spray of 
the feed water as it falls upon the filtering substance below’. 

Charcoal, cobble stones, shavings or whatever is best adapted to take up 
the particular impurities in the water may be used as filtering material. 
I he w ater percolating through the filter passes to the bottom of the heater 
and through the opening in the lower end of the pipe (G) to the boiler feed 
pipe (B) which extends to nearly the surface of the water in the heater, 
when the feed water is taken to avoid taking any oil that might run in on 
the surface as well as take any impurities which may have settled in the 
bottom of the heater. The impurities may be blown off through the blow 
off cock (F). The uncondensed steam passes out of the heater at (E). 

Convenient man holes and doors are provided for the supplying and re¬ 
moving of filtei’ing material. 

The heaters are simple, practical and efficient. They heat the water to a 
temperature near the boiling point besides thoroughly purirying it. 























































































































































pure 8. 

























































































































CIRCULAR OF MALTER, LIND & ROGERS. 


23 


CONTINUOUS WORKING TAILING CON- * 
CENTRATOR. 

The engraving on next page shows the longitudinal sec¬ 
tion of the continuous working apparatus, for the concen¬ 
tration of ore tailings. It consists of one or more cylin¬ 
drical vessels placed in upright positions, having funnel- 
shaped bottoms. When more than one vessel is used, they 
are placed in a row, in order to pass the ore from one to the 
other, each succeeding one being increased in size. The ore 
to be concentrated is introduced by means of a spout, on one 
side of the vessel at its upper rim. 

An upright pipe is suspended to the center of the vessel 
for the purpose of introducing a steady stream of clear 
water, just above the lowest point of the funnel. The lower 
end of this pipe is held in place by means of a spider. 

This upright pipe serves as shaft, to which stirrers are 
attached, which can be made to revolve with the upright 
pipe The shaft is used for the purpose of putting the mass 
ore of pulp in the vessel into rotating motion. 

At a point a few inches below the level of the top of the 
vessel, is a discharge bowl. It encircles the upright shaft, 
and is there supported. 

A spout is secured into the side of the discharge bowl, and 
serves in leading the overflow or tailings, from each vessel 
away, or into the next or succeeding vessel. 

At the bottom of the funnel, is attached an outlet pipe 
for the concentrated sands. The end of the pipe is fitted 
with a valve, in order to regulate the size of the discharge 
opening; the pipe itself so swivels, that the discharge can 
be raised or lowered, and the output facilities increased or 
retarded by controlling the quantity of water it passes out, 
and serves as an agent to carry away the concentrates. 

As the ore to be concentrated falls over the side of the 
vessel into the water contained in it, it sinks down towards 


the bottom, and the coarser and heavier with more force 
than the finer and lighter, as it passes toward the bottom of 
the cone, it meets the clear water, introduced there, which 
creates a rising current carrying upward toward the dis¬ 
charge bowl the light material, while the heavy sinks 
through it into the discharge pipe. If the stirrer arms are 
set in motion they cause the heavier particles of ore to 
gather about the circumference of the vessel, leaving the 
finer and lighter portions near its center, where an upward 
current carries them into the bowl, while the downward 
tendency of the coarser is stronger at the circumference of 
the vessel, the upward current is greatest at the center. 

The great advantage of this apparatus over any similar 
apparatus or any other contrivance for concentrating, con¬ 
sists in its simplicity, cheapness of the construction and 
operation, and durability, its efficacy and the ease 
with which it can be adjusted. The amount of water 
introduced at the bottom of the funnel, and the rais¬ 
ing and lowering of the discharge pipe entirely controls the 
degree of concentration. 

The apparatus is easily attached to any silver mill, as it 
serves efficiently to separate the valuable from the worthless 
tailings, without cost of operation. In mills where the ore 
is being concentrated on tables, or other concentrators, this 
apparatus will be found very efficient, in preparing ore, 
before concentration, and by making it separate the 
coarser from the finer. For all concentrating apparatuses, 
which work on the principles of inclined planes, it will be 
found to concentrate cleaner and to a higher percentage. 

If the ore is first separated in the above apparatus, ac¬ 
cording to size and weight, this apparatus serves in separating 
the light and fine worthless sands of the surplus water, 
from the valuable portion of the ore, thus diminishing the 
quantity decreasing the number of concentrating machines, 
required in final concentration. 




•24 


CIRCULAR OF MALTER, LIND k ROGERS. 



MALTER’S PATENT TAILING CONCENTRATORS. 


















































































































































Pb/\TE 



!< 

3 

23 

Li 


< 

l- 

if] 

>“ 

| 

l n 

a 

UJ 

DC 

a 


1/5 

Cc 

UJ 

la 

O 

cc 


& 


- ^ n; 


Z 

Q 
-J 

□ 
ua 


a 

z 


tt 


o 

O'V >' K 

< J ? 
.ctr * 


uj C'v 

b 

< 

Z 









































































































CIRCULAR OF MALTER. LIND & ROGERS. 


25 


SMELTING OF ORES. 

Argentiferous lead and copper ores containing more than 
fifteen per cent of base metal, can be more advantageously 
reduced by smelting than by the milling process. 

If they are rich enough in base metal, and contain a gan- 
gue favorable to forming desirable slags, or. if fluxes can be 
easily and cheaply obtained, such ores can be smelted with¬ 
out concentration; otherwise, they can be concentrated at an 
expense of 50 cents to SI per ton previous to being smelted. 

“ For the smelting of such ores, and for the redaction of 
all other lead and silver ores, ive furnish complete plants 
and erect them at the mines." As regards the concentration 
of ores, we refer to our remarks on the process of concentra¬ 
tion and the machinery therefore. 

Either reverberatory or blast furnaces may be used to 
matte the metals and separate them from the gangue, of either 
the ores or their concentrates. The reverberatory has some 
advantages over the latter furnace, especially in copper 
smelting, it is, however, seldom used in our mining districts, 
for the reason that onh' ores of a peculiar character can be 
smelted in it with profit, and that such ores are rare on this 
continent. 

The principal advantages of the reverberatory furnace 
over the blast furnace are: 

1st. No blowing engines or pressure blowers are required. 

2d. Raw fuel can be used. 

3d. The manipulation is easier to be controlled. 

The ores best suited for smelting in reverberatory furn¬ 
aces are those of a high grade with calcareous gangue con¬ 
taining none or but a limited amount of refractory metals. 

Lead ores containing considerable zinc, copper, antimony, 
arsenic, etc., cause the formation of rich residues, and often 
also a volitization of the precious metals which the ore may 
contain. 


Silicious ores, containing more than five per cent of quartz, 
are entirely unfit for the reduction by reverberatory process, 
as silicate of lead is formed which impedes the operation and 
causes great loss in residues, unless these residues are 
resmelted in blast furnaces, and then the double process en¬ 
tails great additional expense. The blast furnace process of 
smelting both lead and copper ores is almost exclusively 
used at our mines. The high prices of labor and the refrac¬ 
tory character of our ores make it a more desirable process 
than the use of the English reverberatory just referred to. 

In order to smelt ores successfully, it is necessary to first 
ascertain the mineralogical character and the chemical prop¬ 
erties of the gangue. 

© © 

A mechanical separation of the matrix from the metallic 
portion of the ore, and perhaps a preparatory roasting of the 
ore, should precede the smelting in all cases where the per¬ 
centage of metal in the ores is low, and where the fluxing is 
expensive and a pure and marketable bullion cannot other¬ 
wise be obtained. By concentration it is possible to get rid 
of zinc blend, which causes loss and trouble in the furnace, 
and of a great portion of the gangue, which it would be ex¬ 
pensive to flux and reduce to a slag in the furnace. 

Quartz is infusible by itself and so is lime ; but if the two 
are mixed in proper proportion and exposed to the necessary 
heat, a fusible compound results. Experience has shown 
that the single compounds of silica and lime, or of alumina, 
magnesia, etc., are less fusible than the double compounds 
of, say silicate of lime and silicate of alumina. When replac¬ 
ing one of these bases by alkalies or the proto-oxides of 
heavy metals as, for instance, iron or manganese, the fusibil¬ 
ity of the slag may be increased within certain limits, it 
depends principally upon the proportion of the oxygen in 
the silica to the oxygen in the bases contained in it. 






26 


CIRCULAR OF MALTER, LIND A ROGERS. 


Fluxes are mineral substances which serve to liquify 
others not fusible by themselves. It sometimes occurs that 
an ore contains all the slag-forming ingredients in proper 
proportions, as for example, most of the ores of Eureka 
District, Nevada. 

The usual bases of slags are lime, iron-oxide, alumina, 
magnesia, manganese-oxide, zinc-oxide, some alkalies from 
the ashes of the fuel, etc. 

Silicic acid - - - (Si. o, 3) 21| silicium to 24 parts oxygen. 

Lime.(Ca. o,) 20 calcium to 8 “ 

Proto-oxide of iron (Fe. o,) 28 iron to 8 “ “ 

Magnesia - - - - (Mg. o,) 12 magnesia to 8 

With the assistance of the above formulae it will be easy 
to compute the percentage of oxygen in the bases and acid of 
slags. According to the proportion existing between the 
oxygen of the silica and the oxygen of the bases, four classes 
of fusible slags are distinguished. If the constitution of 
silicic acid is considered to be Si.o, 2, of course the denotation 
of the slags mentioned below would be changed. 

First —Tri-silicates, in which the silica contains three 
times the amount of the oxygen present in the bases. As 
there is over fifty per cent of silica in such slags, they re¬ 
quire too high a temperature for their formation to be feas¬ 
ible in lead smelting. 

Second —Bi-silicates contain generally fifty per cent of 
silicic acid and fifty per cent of the bases, the amount of 
oxygen in the silica being twice that in the bases. 

Third —Singulo-silicates averaging thirty per cent silicic 
acid, seventy per cent bases—the amount of oxygen in 
silica and bases being equal. 

Fourth —Sub-silicates with twenty per cent silicic acid 
and eighty per cent bases, the amount of oxygen being less 
in the silica than in the bases. 


The latter two slags are termed “ basic slags ” because the 
bases predominate in them over the silicic acid. The former 
two are termed “acid slags” because the acid predominates in 
them. Complicated formulae, for the fluxing of ores, have 
been established from accurate analysis of various slags, but 
as the ores or their slags are rarely constant compounds, 
these formulae have little practical value for the smelter, 
who is generally content to know the percentage of silica 
in the ore, and the quantity of useful metal which he is en¬ 
deavoring to obtain. The practical smelter, generally guesses 
at the flux required, by the appearance of his slag in both 
the fused or solid states. An occasional analysis is usually 
deemed sufficient when the ore is of uniform character, and 
when the appearance of the most favorable slag is once es¬ 
tablished and known to the manipulator of the furnace. 
The carelessness of smelters, in neglecting to constantly 
analyze their ores and slag, and to vary their fluxes accord¬ 
ingly, has caused the immense loss of precious metals at 
most of the western smelting works. 

The most desirable slag for lead smelting is the singulo- 
silicate or a mixture of bi-silicate with the former proto¬ 
oxide of iron prevailing in the bases. Such singulo silicate 
slag runs with a bright red color, and solidifies very quickly 
with turgescence. The bubbles when bursting discharge 
bluish gases, sometimes flames. These slags have a vitre¬ 
ous metallic luster and a higher specific gravity than the 
bi-silicates and are therefore more liable to entangle metallic 
particles. 

If lime and alumina are the prevalent bases, the heat 
required for their formation is much higher than if proto¬ 
oxide of iron prevails, and the slags form incohesive lumps, 
run short and pasty. After solidification, they appear honey¬ 
combed or like pumice stone, grayish-green in color, with a 
radiated or laminar crystalline structure. 





4D STAMP WET CRUSHING STAMP MIUU. 

8 UMjT FOR 10. 

GRAt'lb ?EfJrR/\L N|INg. <Jo, 

TONigSToHC. at 
er 

MALTER, LIND Sc ROGERS. 

?aN fK^O^Co, 
qal* Ij5-/\- 

I'TH. iyirf-fON s. REV, J.F. 























































































































































CIRCULAR OF MAI 


An earthy singulo-silicate slag is the least desirable for 
the lead smelter. Bi-silicates form under a higher temper¬ 
ature, and consequently involve a larger consumption of fuel 
than the singulo-silicates. They How slowly like molasses, 
solidify but gradually, without cracking or bursting, and are 
not so liable to form accretions in the furnace as the basic 
slags. After solidifying, they appear vitreous, have a con- 
coidal fracture, and are generally of a blackish color. Being 
saturated with silicious acid, they do not corrode the furnace 
lining as much as the basic slags; their specific gravity is 
lower and metallic particles separate more easily from them, 
but they are apt to take up oxide of lead and cause a loss of 
that metal. 

Th v formation of sub-silicate slags should hr avoided as 
they are very detrimental to lead smelting. They have a 
high specific gravity, and very apt to form accretions in the 
furnace and attack the lining, thus shortening the time of a 
furnace run sometimes to a few days if there is no water 
jacket to the furnace, besides they don t permit a clean sep¬ 
aration from the metal. If proto-oxide of iron is their prin¬ 
cipal base they run in streams like Huid litharge and congeal 
very quickly. 

As fiuxes, the following substances are used : 

First —Iron-stone is a very efficient agent to slag, quartz 
being reduced in the furnace to proto-oxide of iron which 
has a strong affinity for quartz, and forms an easily fusible 
slag. The best quality of iron-stone is hematite or magne¬ 
tite. Hydrated iron ores are very easily reduced to metallic 
iron, and, therefore, should be burned or partially roasted 
before being put into the furnaces. If free from quartz or 
slag, iron-stone may be put into the furnace in pieces as 
large as a man’s fist. Iron ores are also used as desulphur¬ 
izing agents. 


UNI) & ROGERS. 


'17 


Second —Soda, alkalies and potassium, which are obtain¬ 
able in rare cases, are even better than iron-stone as a solv¬ 
ing agent of quartz. They are not used, being rare and 
commanding too high a price. 

Third —Lime is a partial substitute for iron-stone as a 
solving agent for quartz. It should be reduced to the size 
of pigeon eggs. Burnt lime is also used and is theoretically 
better, but is apt to crumble into fine dust which is either 
blownout the of topof the furnace or too readily falls through 
interstices of coal and ore, and does not always unite at the 
proper time and in the proper proportions with the silcia. 
Lime alone cannot be used as a slaging agent for quartz. 
Lime slag is smeary, does not How well, is apt to clog 
the furnace, and the metal does not separate easily from it. 

Fourth —Clay can only be used in small quantities as a 
partial substitute for quartz; it is apt to go to the bottom 
of the furnace without uniting with a base, and there forms 
incandescent lumps which attach themselves to the walls 
anti hearth of the furnace. 

Fifth —Salt, which in some parts of this country is very 
abundant, should not be used as a Hux, being worse than 
useless. It does not unite with the gangue but forms a very 
light slag by itself, which Hoats on top of the other slags. 
Besides, salt may form volatile chlorides of lead and silver, 
thus causing loss of metal. 

Sixth —Iron pyrites, if thoroughly roasted, are a good 
Hux, but if used raw, have no action on the gangue, but 
produce a brittle sulphuretted metal or matte. 

Seventh —Quartz, in form of gravel could be used to fur¬ 
nish acid for the slag where the gangue of the ore is basic. 

Eighth —Acid slags may be used to take up bases and act 
as solvent agents. 

Ninth —Basic slags are used to unite with quartz and act 
as diluting agents. 






2S 


CIRCULAR OF MALT 


Tenth —Metallic iron is used in form of scraps—small 
pieces of wrought or cast iron—to decompose galena, thereby 
forming sulphuret of iron (iron-matte) and metallic lead, 
thus rendering a previous roasting of galena ores unneces¬ 
sary; if there is silver in the ore a great deal of it would 
go into the matte. 

Eleventh —Litharge mav be used in fluxing silver ores, 
which are poor m lead, to prevent the silver from going 
into the matte. 

Twelfth —Cinders or semi-fused matte resultant from 
previous smelting, may serve to extract the metal. 

The fuel most generally used in the blast furnace is char¬ 
coal. Coal burnt of the nut-pine is considered the best. 

Coke can be used to much advantage, but it requires a 
greater pressure of blast than charcoal to effect its perfect 
combustion. 

The pressure blowers generally used to supply the blast 
for copper or lead furnaces, are not always sufficient to 
permit of the economical use of coke. 

One ton of coke produces about the same effect as two 
hundred bushel of charcoal. Fine ore generally requires 
more fuel than coarse ore. 

The amount of fuel required to smelt one ton of ore, of 
course, depends upon the character of the coal, the ore, the 
fluxes, and the construction and manipulation of the 
furnace. 

Xone but pure quartz sand should be used in tire-proof 
mortar around copper furnaces, and nothing but fire dag 
around le<id furnaces. Lime mortar is not fit to be used 
as it crumbles off in the heat, combines with the slag and 
allows it to creep through the joints. The stones or tire 
bricks must be laid as close as possible and all large joints 
must be avoided. The area of the hearth is now generally 
made about half that of the throat, and even less. Small 
furnaces usually have a circular form of cross section. 


LIND M ROGERS 


Larger furnaces are more frequently made oblong in their 
cross sections as the blast can be better divided through 
the ore. Practice has shown that the loss of metal in the 
slag is less in oblong furnaces, than in round ones, under 
otherwise similar circumstances and conditions. The 
number of tuyeres and their position determine in a great 
measure the successful working of a furnace. At the level 
of the tuyeres, the temperature of the furnace is 
highest and the separation of the the metal from the 
gangue, and the formation of matte and slag takes place 
there, the heavier metal sinking downward, the slag 
swimming on top of it. If the tuyeres are placed too low 
the heat will be to great near the surface of the molten 
metal which may cause a great loss in volitization of 
metal. The lowest point of the hearth must not be too far 
below the level of the tuyeres, as the metal may get too 
cold to be drawn of!; thirty to forty inches is about 
a proper depth of hearth for lead smelting, and for copper 
about eighteen to twenty-tour inches. The number of tuy- 
eres must be in proportion to the size of the furnace, depend¬ 
ing somewhat on the character of the ore and the pressure 
of the blast used. About two inches of tuyere area to one 
square foot of hearth area is a standard proportion. The 
height of the furnace above the tuyeres is rarely less than 
ten feet, and considerable more if a high heat is desired. 







TEN STAMP SILVER MILL, 

WITH 

PAN AMALGAMATION. 

BUikT BY 

MALTER> tflND X ROGERS, 

Cal- l)*A* 

N. / 

l>r, * Rif >,f. 



















































































































































CIRCULAR OF MALTER, LIND & ROGERS. 


The furnaces must be low if basic ores are to be smelted, 
especially if they carry a great deal of oxide of iron which 
might be reduced to metallic iron in the great heat of a 
higher furnace. 

High furnaces are required for argillaceous or quartz ores 
where a bi-silicate slag is desired. In high furnaces, a higher 
temperature may be obtained at a less expense in fuel than 
is possible in low furnaces. High furnaces economize fuel, 
but a low furnace is easier manipulated when deranged than 
a high one. Where the character of the ore constantly 
changes, a low furnace is preferable for that reason. 

The manner of feeding or charging a furnace effects its 

work materially. The ore, fuel and fluxes must be intro- 

«/ * 

duced in proper proportions and spread uniformily over the 
top. 

Charge scales, so-called, should always be used, upon which 
the ore, fuel and duxes can be weighed without any change 
of weights. The metallurgist, after having determined the 
proportions of the materials to be charged, sets the scales, 
and the furnace feeder has nothing more to do but to place 
the charge car upon the scales and load it until it balances 
for each material. All guess work is thus avoided and a 
uniform result is ensured. 


29 


Cuts 3 and 4 show a charge car. It rolls upon rails which 
extend over the top of furnace and the scales. The car, 
after having been loaded on the scales, is placed over the 
shaft of the furnace, the lever which lifts the sides is pressed 
down by the foot, and the charge drops out beneath them 
in form of a perfect circle, uniformly spreading over the top 
of the furnace. Smaller furnaces, having the smoke-stack 
on top, are generally provided with a feed-hole in their side 
just beneath the stack ; through this hole the materials to 
be charged are introduced by means of a shovel. This is 
not a desirable method, and may give rise to a great many 
irregularities if the feeder is in the least careless. 



No. 3 


Charg-e Car. 


No. 4 
























































































CIRCULAR OF MALTER, LIND & ROGERS}. 


.SO 


The smoke and the fumes of the furnace can he carried 
away either by a smoke-stack placed directly on top of the 
furnace, or by a Hue, which may start from the side or 
from the top of the furnace, and extend horizontally to a 
chimney. Several furnaces may be thus connected with one 
chimney. These connecting flues may also serve as dust 
chambers. Funnel shaped chambers are often attached to 
them extending downward and having a gate at the lowest 
point; the accumulated dust can be readily taken from them. 
Wh en the ore is fine, the furnace low, and a strong blast is 
used, a great deal of dust may be carried away with the 
flumes, and a considerable loss occur in this way, which can 
be overcome, in a measure, by these flue chambers. 

A new furnace must be heated gradually, to permit the 
moisture in the masonry to escape; several days or weeks, 
may be consumed in drying a new furnace. After drying 
is finished, the bottom stone is covered with fire-clay, the 
lead-well and the top holes are lined, and the dam covered 
with fire proof material. 

Most all lead furnaces are now provided with lead- 
wells, or so-called syphon-taps. The formation of “ sows ” 
is in a great measure, prevented by the automatic syphon- 
tap, which carries the molten lead continuously out from 
the bottom of the furnace as fast as it is reduced in¬ 
side, and if much of the iron in the furnace be reduced to 
metallic state, it will swim on top of the lead, always at the 
same level. It can never reach the bottom of the furnace, 
but remains exposed to the oxidizing influence of the blast, 
which causes it to be carried into the slag. 

As the automatic syphon taps the furnace at its bottom, 
none but the heaviest metal is being carried out; iron and 
zinc, etc., being lighter than lead, swim on the surface of the 
molten mass ; and are kept exposed to the oxidizing heat of 
the blast, thus being largely carried off in the slag. 


Carbonate ores, if they contain the slag favoring ingred¬ 
ients, will often produce pure metal without further fluxing, 
but Galena ores, although they contain all favorable slag 
ingredients, must be fluxed with metallic iron to absorb the 
sulphur of the galena, to produce metallic lead; or if not so 
fluxed, the galena ores must be subjected to a roasting or 
calcining operation before smelting them. 

Sulphuretted copper ores cannot be well fluxed with iron, 
as the iron matte which would result could not be easily 
parted from the copper, therefore such ores should be cal 
cined or roasted to enrich the matte. This is best done 
after the ores are pulverized, in a reverberatory furnace, but 
as tine pulverized ores cannot be well smelted in a blast fur¬ 
nace, either reverberatory smelting furnaces are used, as is 
done in Butte, Montana, or the ore is roasted and pulverized 
and made into adobies—in brick form—and then smelted in a 
blast furnace. Attempts to roast highly sulphuretted copper 
ores in heaps without previously pulverizing them, do not 
generally give satisfactory results. The calcining furnace 
shown in engraving on page 35, is best suited for the roast¬ 
ing of ores in lumps, and will give more satisfactory results 
than roasting the ore in heaps. 

If the sulphuretted ores are crushed and roasted in a rever¬ 
beratory furnace, the heat can be increased at the finish of 

1/ 1 

the roasting so as to partly melt the roasted ore and form 
lumps, which can be broken into convenient pieces for smelt¬ 
ing. 

Ores yielding a very basic slag may be introduced into 
the furnace in large pieces, and still be easily smelted ; sili- 
cious and calcareous ores ought to be crushed in rolls, or at 
least in rock breakers, to the size of eggs. 






PLATE 12- grpi/Nd pLa>| of 

TWENTY 5TAMP SIUVER MIUli WITH 


TAILING CONCENTRATORS. 

BUiLTBY MAlfTER, UIND £ ROGERS. 

jat) |Hpci5Co. 





























































































































































































































































































































































































31 


CIRCULAR OF MALTER, LIND & ROGERS. 


Metallic iron does not always find heat enough in lead 

t «< O 

furnaces to be run out with the slag, and hence is apt to 
congeal in the hearth, and forms what the smelter calls 
“ sows ” or “ horses,” etc. Very tine ores should be worked 
into adobes (unburnt bricks) like the pulverized and roasted 
ores, to prevent their getting about the tuyeres, choking the 
blast and deranging the furnace. An ordinary brick ma¬ 
chine does not answer the purpose of making these bricks, 
as they are apt to crumble too easily if not made under 
heavy pressure. We can furnish proper brick machines at 
a cost of from one thousand to three thousand dollars, capa¬ 
ble of making from ten thousand to fifty thousand bricks 
daily. 

The Hesse smelting furnace is one of the best constructed 
and equipped furnaces in use in our mining regions. The cut 
on next page shows a sectional view of it. The water jackets 
are made in sections secured together in such manner that 
any portion of it can be taken down without disturbing the 
rest. This jacket does not extend in height as much as is 
generally the practice in furnace building. Several courses 
of brick clamped together in sections, find room above it, 
and below the iron plate that supports the upper portion of 
the furnace. In case the furnace becomes deranged from 
anv cause whatever one or more of these sections of brick 
can be easily removed and the furnace can be entered with 
crow bars, etc. 

The steam that may be generated in the jacket is carried 
way by pipes. 

The molten lead is not dipped from the lead well, as is 
ordinarily done, but an automatic ladle is so arranged upon 
a turn table that the bullion mold may be filled without 
lifting the lead. 


There are many refractory ores of complicated mineral- 
ogical character which might be reduced by smelting as well 
as by leaching or by amalgamating processes. 

To assist mining men in selecting the process by which 
such ores may be best reduced we will describe the ores and 
works of the Gregory MiningCoinpany, giving the cost and 
the result of the reductions, and consider the various ways 
in which the ore might be worked. 

Gregory mines contain about, 

O %J 

Ten to twelve per cent of galena. 

Eight per cent of arseno-pyrites. 

Six to twelve per cent of iron and copper pyrites. 

“ “ “ “ “ zinc blende. 

Sixty to sixty-five per cent of quartz. 

A ton of the galena ore carries about twenty dollars of 
silver. A ton of the arseno-pyrites carries about fifteen dol¬ 
lars of gold. 

The iron and copper pyrites carry but a trace of gold and 
silver. 

The zinc blende, and the quartz hold no valuable metals. 

When running full capacity the Gregory Company reduce 
100 tons of this refractory ore per day, producing copper 
matte and lead bullion carrying the precious metal. 

The works consist of a concentrating mill having 150 
tons capacity per day. Six reverberatory roasting furnaces. 
One Hesse smelting furnace. 

To smelt the Gregory ore without previous concentration 
would not be possible, at least could not be made profitable, 
as nearly ninety per cent of the ore would have to be got¬ 
ten rid of in the smelter, and as nearly an equal amount of 
flux would have to be added to the ore to make its reduction 
feasible. 




Sectional View of the Hesse Smelting- Furnace 


CIRCULAR OF MALTER, LIND & ROGERS. 















































































































































































































































































pu/\te: 1 4 




rftONlT ETLeV/\TIOH or 

FDRTY STAMP WET CRUSHING 

SILVER MILL, 

5 (Jilt 

MALTER, UIND £ ROGERS. 

r pA ^'y r-0 . 

Qau (jj^ 

Uttf-MiffoN r Key. 5-f- 


















































































































































































































CIRCULAR OF MALTER, LIND & ROGERS. 


33 


The fuel required to smelt this great amount of material 
would probably exceed the value contained in the ore. 

The concentration of the ore greatly cheapens the subse¬ 
quent extraction of the precious metal, although the ore be 
of a character difficult to be concentrated. The quartz of 
the Gregory ore is extremely hard, and the metal very linely 
divided through it, hence the ore must be crushed very tine 
to separate the metal from the gangue. 

Fine crushing produces a large amount of slimes, even if 
the crushing is done by pressure in rigid rolls and breakers 
in which all grinding action is avoided. Slimes cannot be 
easily concentrated They are separated by our slime sepa¬ 
rators from the coarser tailings and the finer quartz, and 
gathered in a reservoir, where they are permitted to settle ; 
the clear water is then pumped back from the reservoirs to 
be used over and over again. If this water was permitted 
to run away, it would carry the slimes with it. 

Owing to the difficulty of concentrating the Gregory ore> 
the company were compelled to discard their old concentrat¬ 
ing mill with cornish rolls and Collum jigs, and to build new 
works of our construction and improved machinery, which 
thoroughly reduce the ores at a very small cost. 

The Gregory Company have six reverberatory furnaces of 
the construction shown on page 35. 

The capacity of each furnace is six tons of concentrates 
per day of twenty-four hours. The roasting is a dead roast¬ 
ing , and its cost is a little less than four dollars per ton of 
concentrates. 

The revolving furnaces are not suitable for the purpose of 
dead roasting ores since much time is required, and hence 
much power would be expended in keeping the furnace in 
motion with its mass of ore, and a large percentage of the 
roasting ore would be raised as dust in consequence of the 
continuous action of the revolving furnace; this valuable 
^ust would be carried into the dust chamber and perhaps out 


of the chimney, it would at least be partly lost and probably 
insufficiently masted for further working. With ehloridizing 
roasting, it is otherwise, revolving furnaces do such roasting 
well enough, much less time being required to produce 
chlorides than oxides, and hence less motive power is 
consumed by the shorter work and less dust made. 

Each furnace at the Gregory consumes daily two cords of 
wood, costing four dollars per cord ; and four men are re¬ 
quired to attend to them,two in day and two at night. About 
three hundred pounds of pulverized charcoal (sifted refuse) 
are added for each furnace charge, to prevent the formation 
of arseniates, and to prevent ore from adhereing to the 
hearth. 

The benefits derived from the dead roasting are: 

First .—Nearly all of the arsenic is expelled. 

Second .—The galena is largely converted into oxides of 
lead. 

Th ird .—The iron and copper pyrites are reduced to oxides; 
the iron forms a Mux for the quartz, and the copper makes a 
valuable matte. 

If the ore were not roasted previous to being smelted, no 
metallic lead could be produced, and a good deal of very ex¬ 
pensive iron and lime fluxing would be requred, which be¬ 
comes unnecessary after driving oft’ the sulphur by roasting. 

The Hesse furnace has a capacity for reducing daily from 
twenty-five to thirty tons of roasted concentrates, which 
yield seven to eight tons of bullion, and five per cent of 
copper matte. The cost of reduction is nine dollars per ton 
of concentrates, charcoal for smelting purposes being worth 
twenty-five cents jier bushel, and coke, twenty dollars per 
ton. 


Water Jacket Smelting Furnace. 


CIRCULAR OF MALTER, LIN]) & ROGERS? 



























































































































































CIRCULAR OF MALTER, LIND A ROGERS. 


36 


THE ADVANTAGES AND DISADVANTAGES OF 
WORKING REBELLIOUS ORES BY VARIOUS 
PROCESSES. 


The copper matte is crushed, roasted in kilns, and passed 
through the blast furnace two or three times with the con¬ 
centrates until a high grade copper matte results. The bullion 
contains never less than ninety-five per cent of all the gold 
and silver which was in the concentrates; it is worth about 
four hundred and fifty dollars per ton. Assuming the ore 
to have been worth thirty-five dollars per ton in gold and 
silver, which is about its value outside of the lead, and re¬ 
ducing fifteen tons of ore to one ton of bullion worth four 
hundred and fifty dollars, it will be seen that seventy-five 
dollars have been lost out of the total value of the precious 
metal contained in fifteen tons. This is a loss of five dollars 
per ton in precious metal. And since the value of the lead 
enhances the value of the metal resulting from the working 
of 15 tons of ore and is included in the 450 dollars, the loss 
per ton of ore by this process of working appears even 
more than five dollars per ton. However, the loss is not so 
great since the slimes contained in the reservoir are valuable, 
as is also the copper matte. The slimes are roasted, made 
in adobes, and smelted; the copper matte is saleable 

The entire cost of reduction of the ore sums up as follows : 

Concentrating one ton of ore into 500 pounds of concen¬ 
trates, costs $1. 

Roasting of one ton of concentrates costs approximately 
four dollars, there being four tons of ore reduced to one ton 
of concentrates makes cost for one ton of ore equal to $1. 

Smelting at cost of nine dollars per ton for roasted con¬ 
centrates which equals two and one-half dollars per ton of 
ore ($2.50), (10 per cent of weight being lost in roasting). 

Total cost for working one ton of ore $4.50. 


Although the Gregory ore contains a large amount of base 
metal, it might be worked by the dry-crushing mill and 
amalgamating process. Mettalurgists have frequently un¬ 
dertaken to reduce equally refractory and base ores by that 
process. 

The cost of working such ores by that process, would be 
about 15 dollars per ton. At least ten per cent of salt would 
be required for the chloridizing roasting, in order to con¬ 
vert both the precious and the base metals into chlorides, 
for the base metals must be either chloridized or oxidized 
before the precious metal, the silver, can be converted into 
chlorides. 

It would probably be impossible to save any appreciable 
percentage of the gold by the amalgamation process after 
roasting the ore. Gold does not generally amalgamate well 
if the ore has been previously roasted, and since gold consti¬ 
tutes 40 per cent of the value of the ore, its loss if amalga¬ 
mation prove insufficient, would make the working of the 
ore unprofitable. 

To reduce one hundred tons of ore (as do the Gregory 
works) by dry-mill process, would require a sixty stamp-mill, 
the first cost of which is much more than the Gregorv works. 

The wear and tear, and the consequent cost of repairs and 
depreciation of value of the reduction plant, is twice as 
great in a Dry Crushing Mill as in a concentration and smelt¬ 
ing works. All the value of lead and copper in the ore 
would be lost. The bullion resulting from the amalgamation 
process would contain but a small portion of it, and that in 
a manner which depieciates the value of the bullion rather 
than enhances it, lead and copper being an alloy with 
the silver. 






SECTIONAL VIEW 

—OF— 

SMELTING WORKS 

—AT— 

La Trindad 
Mines, Mexico. 

—built by— 

MALTER, LIND & ROGERS. 


























































































































































































































































































CIRCULAR OF MALTER, LIND & ROGERS. 


38 


The base metals might be leached off in part with water, after 
having been converted into chlorides by roasting, previous 
to amalgamation of the silver in the pans, but this would 
add expense in labor, and probably loss in silver. Chlorides 
of lead cannot be very well leached out of silver ores. 

Considering the above disadvantages and difficulties, it is 
quite evident that ore of the value and character of the 
Gregory ores could not be reduced properly in a dry crushing 
and amalgamating mill. 

It has frequently been undertaken to extract the precious 
metals from such ores as the Gregory, by lixiviation. The 
preparation of the ores for the lixiviation process, consists in 
crushing them finely in a dry crushing stamp battery as is 
done for the roasting and amalgamating process ; then the 
ores are subjected to a chloridizing roasting, and afterwards 
put into leaching tanks where the silver is leached out by a 
solution of hyposulphates of soda or lime. The ore would 
then have to be dried and chlorinated to convert the gold in 
it into soluble condition, and to make possible its extraction 
by leaching. 

This process, of course, is quite complicated, and in all 
probability, would not yield as high a percentage of the 
precious metal as the concentration and smelting process. 

The cost of working the ore by leaching process, could 
not be less than ten dollars per ton if the ores were not con¬ 
centrated before roasting and leaching. If concentrated the 
cost of the lixiviation process might not exceed the cost of 
the smelting process per ton of ore worked. The value of 
the base metals, lead and copper, would be lost in the leach¬ 
ing as well as in amalgamation. Dry crushing the ore finely 
in a stamp battery would cost more than crushing the ore 
coarsely in rolls and concentrating it. 


The chloridizing roasting necessary to prepare the ore for 
the leaching operation could beeffected in automatic furnaces, 
and would require less time than the dead roasting prepara¬ 
tory to smelting, but it would not cost any less since a large 
amount of salt would be required. Then the cost of leach¬ 
ing with water for base metals, and with hyposulphates for 
silver, and employing the chlorination process to extract the 
gold after drying the ore again, would certainly not be less 
expensive, than the mere smelting of the concentrated and 
roasted ore in a furnace. 

The cost of the necessary reduction works for either leach¬ 
ing or smelting is about the same. The consumption of fuel 
is larger in the smelting process; the amount of labor re¬ 
quired, greater in the leaching process. Considering this, it 
remains a question as to which process should receive the 
preference in working ores of the character of the Gregory 
ores. 

This question can only be answered after investigating the 

conditions of the country. Thus in Mexico, where labor is 

«/ 

cheap and fuel expensive, leaching might be given the pref¬ 
erence ; in our northern mining regions, where fuel is found 
in plenty, and labor commands a high price, the smelting 
process might be more advantageous. 










P[i/\TE 15 


FORTY 5TAMP M I Lili 


CDNTINU0L15 WQRKING PAN AMALGAMATION 

jjuilT £y 

. MALTER, LIND S ROGERS. 

Franco, 
































































































































































































































































































































y 















40 


CIRCULAR OF MALTER, LIND & ROGERS. 


THE LIXIVIATION OR LEACHING PROCESS. 


Under this name is understood the extraction of chloride 
of silver from ores by alkaline hyposulphates,which method 
Percy and Hanch proposed in 1850. 

Patera of Joachimsthal, Bohemia, 1858, was the first who 
applied the method in a practical way by using hyposul- 
phate of soda as a solvent for the chloride of silver, and 
polysulphide of sodium as a precipitant, while Kiss, in 
Hungary, I860, used liyposulphate of lime as solvent, and 
polvsulphide of calcium as precipitant. Patera subjects the 
ore before leaching to a very complicated and expensive 
roasting. 

In Kustel & Hoffman’s Modified Leaching Process, which 
was first introduced by them at La Dura, Mexico, in 1868, the 
chloride of silver is dissolved in hypophosphate of soda and 
precipitated with polysulphide of calcium. This modification 
made the leaching process adaptable for our country and Mex¬ 
ico, and it is this modification which is so extensively used 
on this continent. The polysulphide of sodium, as well as the 
hyposulphate of lime are very troublesome to manufacture, 
while polysulphide of calcium is easily prepared (by boiling- 
sulphur, water and lime), and the hyposulphate of soda can 
be bought cheaply in the market. 

The advantage of Kustel’s modification is proved by the 
fact that in none of our numerous leaching works is either 
the Patera nor the Kiss process used as such. 

APPLICABILITY OF THE LEACHING PROCESS. 


This process can be applied to much larger variety of 
ores than amalgamation, in fact most any kind of silver 
ore, no matter how base, winch permits a good chloridizing 
roasting and a good Jilt ration is suitable to be workedby it. 

It is well to ascertain what percentage of silver can be 
chloridized in roasting, as only the chloride of silver can be 


extracted by this method. This can be done by roasting 
one-half ounce of the ore with salt in the muffle After 
the roasting is finished the ore is carefully put into a paper 
filter and leached with water, and then with hyposulphate 
of soda until all the chloride or silver is extracted. Then 
the tailings with the filter are placed in a roasting dish,dried 
and heated in the muffle to burn the filter, and finally fluxed 
in a crucible, and assayed. 

Another one-half ounce of the same sample of raw ore 
has to be assayed from the difference of both results, the 
percentage of the chloridized silver can be calculated. This 
difference also tells us the approximately obtainable percent¬ 
age of silver, less loss in roasting. Usually a better chlorin- 
ation can de obtained bv roasting on a large scale. Roasted 
ore filters much better than raw ore. If an ore contains 
a great deal of clay and is not too rich in silver, a slight 
concentration by which the clay is separated from the ore 
can be obtained from it. 

The advantage of lixivation consists in the cheapness of 
reduction, and the low cost of the plant. No power is re¬ 
quired, except for crushing and roasting, and there is hardly 
any wear and tear, as the vats last many years ; the wood 
being protected by the base metal chlorides from decaying. 
The most favorable feature of the process, however, is its 
applicability to very refractory ores. Of great advantage 
is also the fact, that there is no machinery used, no loss of 
time can occur in the leaching department of a mill on 
account of breakage. There is also no need of stopping the 
operations on account of “ clean up’s,” as one precipitation 
tank after another can be cleaned up while the other tanks 
are working to their full capacity. 





CIRCULAR OF MALTER, LIND & ROGERS. 


39 




MANIPULATION. 


A—ROASTING. 

If no concentration is required, the ore has to be crushed 
dry on account of the subsequent roasting, but only in ex¬ 
ceptional cases is it necessary to pulverize through a liner 
screen than No. 40. Some easily roasted ores, especially 
those which are free or contain but a small percentage of 
zinc blende, will permit a good chloridizing roasting, even if 
pulverized through screen No. 20. Coarse pulp is preferable 
as it improves the filtering capacity of the ore, which 
shortens the time required for extraction. But the roasting 
has always to be the guide for the operator in selecting the 
proper fineness of the pulp. 

In order to chloridize the silver, the ore has to be roasted 
with an addition of common salt. To roast successfully a 
sufficient quantity of sulphurets must be present in the ore, 
as the sulphurets by decomposition, produce sulphuric acid, 
which acts on the salt and liberates the chlorine necessary 
for the formation of silver chloride. The amount of salt to 
be added depends on the character of the ore, and varies 
between five and ten per cent. Rich ore requires more than 
poor ore ; and again, if the same is highly sulphuretted, and 
very base, a higher percentage of salt has to be used. The 
proper amount is easily ascertained. In starting the works 
it is advisable to begin with a higher percentage of salt 
than the character of the ore would justify, and then to 
drop at each successive charge, one per cent, until the point 
is reached where the chlorination begins to suffer. An assay 
and chlorination test of each charge has to be made and the 
result put on record, which will enable the operator, without 
difficulty, to ascertain the necessary amount of salt. 


The salt ought not to be coarser than the pulp, and should 
be well mixed with the same before charoino- the furnace. 

O O 

This is done either by crushing the ore and salt together, or 
better by crushing the salt separate and adding it contin¬ 
uously by means of a salt-feeding machine into the convey¬ 
or, where the screw will perform a very thorough mixing. 
By using continually discharging furnaces this previous mix¬ 
ing is a necessity, while with charge furnaces it has the ad- 
vantages that, if lumps are formed in roasting, the same will 
be chloridized too, as the salt is divided through them. In 
cases where the ore bakes easily on a little increase of heat, 
it might be found advisable to add the salt after the forma¬ 
tion of sulphates take place, but to do this, in order to di¬ 
minish the loss of silver in roasting, is an operation which 
should be performed only if it is actually found to have the 
desired effect, as in most intances, no better result will be 
obtained by it, but on the contrary, will often be the cause 
of a lower chlorination, an increase of flue dust, and extra 
labor. This is not the case, however, if the oxidizing roasting 
is continued until all the base metals are converted into ox¬ 
ides and then the salt, and from one to three per cent of 
green vitriol is added. But this mode of roasting is more ex¬ 
pensive on account of the additional use of green vitriol and 
the longer time required to effect oxidizing roasting. 

The mechanical furnaces, almost exclusively in use now, for 
chloridizing roasting are divided into two classes ; those with 
continual feed and discharge, and those which ace fed by 
charges. As the roasting is the most important part of the 
process, the part upon which principally depends the 
good result of the extraction of the silver; it is very 
important to select the right kind of furnace for a 
certain kind of ore, furnaces which are fed by charges 
like the improved Bruckner furnace, are more reliable, 
and can be used for any kind of silver ores, even the 
most rebellious, as the operator has the charges under his 








PLATE 16. 


?e^tioHaU eleV/m'ioH 

OF A 


5D STAMP DRY CRU5HINE MILL, 

W ITH 

ROASTING FURNACES. 

BUILT FOR THE 

/L&XANbEK MiN'K 0 - 

}W 

MALTER, LIND S R06ERS. 

Sty fwCiXo. 

l^H. p|(lT<0H « REYi 








































































































































































































41 




CIRCULAR OF MALTER, LINI) & ROGERS. 


perfect control, and can conduct the roasting according to 
the nature of the ore, while through a continually discharg¬ 
ing furnace the ore passes in a certain given time and the 
operator has to accept the ore as the furnace gives it to him, 
whether the roasting is finished or not, for which reason this 
kind of furnace is applicable to the more easily roasted ores 
only. 

Before charging, the furnace has to be made to revolve, 
and has to be well heated by a gradually increased tire. 
Then the charge doors are opened, and the furnace stopped 
with the doors beneath the hoppers. By pulling the slide of 
the hopper, the whole charge drops from it into the furnace. 
The doors quickly closed, the furnace is set in motion again 
and a strong fire kept up, until the sulphur commences to 
burn well, then the fire is slacked, or if the ore contains so 
much sulphurets that the burning of the sulphur creates too 
great a heat, the fire is stopped entirely, until a falling off 
of the temperature is perceived, Then the fire is started 
again, but the temperature is still kept moderate, until the 
reaction between the sulphates and salt begins, when the 
heat is increased to bright red, and kept so until the chlor¬ 
ination is finished. During the oxidizing period, the formation 
of sulphates takes place. Strong fumes of sulphurous acid, 
and, if present, of antimony and arsenic are evolving from 
the ore, the ore retaining a sandy appearance. As soon as 
the reaction of sulphate and salt commences, the ore increases 
in volume, assumes a wooly consistency, and, while the smell 
of sulphurous acid disappears, that of chlorine is taking its 
place. 






































































































































































CIRCULAR OF MALTER, LIND & ROGERS. 


43 



quired. This pipe is called the air valve, and permits the es¬ 
cape of air from under the filter. 

This is of great service, as it prevents the air from breaking 
holes in the filter, by ascending through the ore. Along the 
front of the leaching tanks, and about 24 inches lower, ex¬ 
tends a gallery four feet wide. On this floor, and about the 
middle of the whole length is placed the distributing tub I. It 
is a flat tub of about 20 to 30 inches diameter, and 12 inches in 
depth. Into this tub is conveyed by means of two troughs 
the silver solution of all the leaching tanks. The bottom of 
the distribution tub is provided with as many lead pipe out¬ 
lets, as there are precipitation tanks. Each outlet can be 
closed with a plug. This arrangement is a very convenient one 
as the operator can merely by pulling one plug, direct the so- 

Cut 26. 


lution to flow into either of the precipitation tanks C C. 
Another trough along the tanks conveys the base metal solu¬ 
tion. In front of the leaching tubs are the precipitation tanks 
and placed in such a way, that the upper rim comes about 18 
inches below the platform, extending about two feet under the 
same. It is well to have about four or five of these tanks, in 
order to give the precipitated silver plenty time to settle. 

Another gallery (not the precipitating floor) is located 
about two feet below the top of these tanks. 

The sulphide of calcium solution is conveyed by means of 
hose from the reservoir to each tank. The flow of the 
solution can be regulated by hose clamps. 








































































































































































































































































































































44 


CIRCULAR OF MALTER, LIND & ROGERS. 


The next lower floor is the filtering floor, which is placed 
about 3 feet, (i inches below the bottom of the precipitation 
tanks. The part of the tanks which reaches below the preci¬ 
pitating floor is provided with one outlet close to the bottom 
for the discharge of the silver, and from three to four others 
in different levels for decanting the clear solution. These 
outlets are also provided with hose and damp, and discharge 
into a trough leading to the pump tank or lower reservoir. 
The filters E E consist of one or more square frames, each of 
which is divided into four squares 3 feet by 3 feet, and 
covered with unbleached cloth, forming in each square a 
filter sack. They are constructed in such a way that the 
dividing scantling between the two filters is provided with a 
cut eighteen inches long and one and one-half inches deep, 
permitting the precipitate, if one filter is full to flow into the 
next, and so on until a whole set is filled. Each set of filters 
is suspended by frame-work above a square fiat tank about 
ten inches deep, into which the filtrate runs, and from there 
it is convey to the pump tank H. 

The material of the tank ought to be two and a half or 
three inches thick; clear lumber for staves and bottoms. In 
dry climates the troughs have to be lined with sheet iron. 

2nd.—Base metal leaching; 

After the leaching tank is charged the outlet hose is placed 
into the base metal trough and a stream of cold water is al¬ 
lowed to flow on the top,which in passing through the ore, dis¬ 
solves the base metal chlorides. In the beginning the out-flow¬ 
ing water is highly charged with base metal salts. If there is 
considerable copper in the ore, the color will be green, and if 
there is lead and antimony, it will have a milky appearance 
from line flakes of chloride of lead and antimony, and some 
silver. This is mostly observed soon after the first concen¬ 
trated liquid has passed off, and the solution becomes less 
concentrated, or, if the concentrated liquid mixes in the base 
metal trough with a stream of diluted base metal solu¬ 


tion coining from another tank. In leaching with water, 
the chlorides of iron, copper, zinc, lead, and antimony are 
removed. These chloride salts, if concentrated, have the 
property of dissolving chloride of silver, which, however, is 
precipated again together with lead and antimony as soon as 
the solution is diluted. 

As mentioned above, the first water from the base metal 
leaching is highly charged with these salts, and consequently 
some chloride of silver will be dissolved by them, but as the 
discharge of the concentrated liquid lasts only a short time, 
the amount of the dissolved silver is small and can easily be 
regained. Mr. Hoffman prevents the escape of this silver 
by admitting the stream of water from below, under the 
false bottom, instead of from above. By pressure, the water 
is forced to ascend through the ore, and the concentrated 
solution appears on top of the ore. Here the solution is di¬ 
luted by a stream of water, and the precipitation of the 
chloride of silver effected. The liquid is now permitted to 
descend through the filter, and the chloride of silver remains 
on and through the ore, and is afterwards extracted with 
the balance of the silver. 

Mr. Stedefelt, in making chlorination tests, made the obser¬ 
vation that, if the sample of roasted ore is leached first with 
water and then with hyposulphide of soda, the result would 
show a higher chlorination than that obtained by leaching 
only with hyposu’phide of soda without previous leaching 
with water. Both observations indicate that considerable 
chlorination takes place during the short time that the base 
metal is leaching. 

The copper can be obtained from the chloride solution by 
precipitating the same with metallic iron, as copper cement, 
or by using as a precipitant, the iron sponge; a finely divided 
iron obtained by heating pulverized iron ore with charcoal 
powder in an iron retort. 



CIRCULAR OF MALTER, LIND & ROGERS. 


45 


I he base metal leaching 1 takes from one to two hours. If 
after adding a few drops of sulphide of calcium to a sample 
of the chloride liquid, only a reddish brown color appears, 
and no precipitate is formed : even if vigorously stirred, the 
leaching with water is finish ad, and the inflow of water on 
the top of the ore stopped. 

At the Silver King Mine, Arizona, the silver carried off’ by 
the base metals was regained by conveying the concentrated 
solution to large tanks, and diluting the same with water, 
the chloride of silver together with the chlorides of lead and 
antimony precipitated and settled to the bottom. The clear 
solution was drawn off* and the tanks charged again till 
enough precipitate is accumulated, when the same is strained, 
dried, and melted together, or with the silver precipitate in 
a cupelling furnace. 

Mr. Kustel used for this purpose, at Flint, Idaho, a large flat 
box provided with partitions G inches apart, in such a way as 
to form a zig-zag trough, which was filled with shavings. 
Through this trough the chloride solution was permitted to 
flow after being diluted with a small stream of water. The 
shavings afford a large amount of surface for the chlorides to 
deposit on. The accumulated white precipitate he placed in 
filtering bags, washed it with water, and extracted the silver 
with hyposulphide of soda. 

It seems that a part of the silver which escapes chlorin¬ 
ation in the furnace is chloridized by action of the base me¬ 
tal chlorides during the process of leaching with water, 
especially if chloride of copper is present. Mr. Hoffman, 
by working the Silver King ore, found by taking samples 
just before the base metal leaching commenced, and after it 
was concluded, that during this process, the original chlorin¬ 
ation of the already moistened ore improved from three to 
seven per cent. As a matter of course, the loss in weight 
which the ore sustains by removing the base metals had been 
taken into consideration. 


3rd.—Silver Leaching : 

As soon as the water disappears from the top of the ore a 
stream of a diluted solution of hyposulphide of soda is con¬ 
veyed into the tank. It is not good to let the water drain 
entirely from the ore before the hyposulphide of soda is let 
in, as in this case, air is sucked into the charge, which after¬ 
wards, partly by ascending breaks little channels in the ore, 
through which the solution runs more swiftly than through 
other places, and partly remains in the ore, forming little 
bubbles, thus preventing the solution from coming in uniform 
contact with all the ore particles. 

If done as described here, the stream of water from under 
the filter will flow undiminished, and is still permitted to flow 
into the base metal trough, but close watch has to be kept, 
and the liquid frequently examined, if it contains silver. 
This is done by adding a few drops of sulphide of calcium 
to a sample of the solution. As soon as the least indication 
of the formation of dark clouds are perceptible, the solution 
contains silver, and the outlet hose has to be placed in the 
silver trough. The presence of silver is indicated too, by 
a sweetish taste in the solution. It takes about fifteen to 
twenty minutes before the silver solution begins to run out, 
but it becomes in a short time highly charged with silver. 
Sulphide of calcium added to the solution causes a heavy 
dark brown precipitate. In a few hours the main part of 
the silver is leached out. The precipitate is now of a more 
reddish brown color, and not as thick and heavy, but still 
carries silver. It contains principally lead and copper. By 
conveying the concentrated and the diluted solution to differ¬ 
ent tanks and treating them separately, two kinds of bullion 
can be obtained if so desired, one very fine, and the other 
very hase. This, however, is not usually done. 





46 


CIRCULAR OF MALTER, LIND A ROGERS. 


In roasting, part of the lead remains in the ore as sulphate 
and part of the copper, as subchloride. These base metals are 
not soluble in water, but are so in a solution of hypos ulph id e 
of soda, and dissolve more readily in a concentrated solution 
than in a diluted one, therefore, it is well to use a diluted so 
lution of about 1-2 to 1. Two pounds of hyposulphide of 
soda, is capable of dissolving one pound of silver. 

Chloride of lime dissolves more easily than the sulphate of 
lead, and the subchlorides of the base metals, consequently, 
after the soluble silver has been extracted, the solution still 
shows, in most cases, a reddish precipitate, caused by the pres¬ 
ence of base metals, if sulphide of calcium is added. This 
reddish silver is extracted, and it is impossible for the oper¬ 
ator to tell by looking at it, when all the silver is extracted, 
and he either does not leach long enough, or too long. This 
either causes a loss of silver, or a loss of time, and in the lat¬ 
ter case, a great deal of base is unnecessarily added to the 
silver precipitate. 

In order to avoid all this, and to enable the operator to 
know the exact time when the leaching should stop, Mr. 
Hoffman introduced the following very simple and quick 
test: 

A tumblerful or two of the solution is precipitated with 
sulphide of calcium. The precipitate is allowed to settle, the 
clear solution decanted, and the precipitate with part of the 
solution poured into a small paper filter. After all the so¬ 
lution has dropped through, the precipitate is washed with 
warm water ; then the filter is taken out of the glass funnel 
and spread out. The precipitate is scraped off with the 
blade of a pocket knife, and introduced into a test tube. 
Some nitric acid is added, and boiled till no more red fumes 
escape. Then the tube is held in cold water to hasten the 
settling of the sulphur. The clear acid is carefully poured 
off from the sulphur into another clean test tube, and a few 
drops of salt water or muriatic acid are added. If a white 


precipitate is formed, water is added and boiled to dissolve 
chloride of lead. 

If the white precipitate remain, or if the solution re¬ 
tain a milky appearance, it is proof that there is still 
some soluble silver left in the ore, and the leaching has 
to be continued. On the other hand, if by the addition of 
salt water no precipitate was formed, or if the white precipi¬ 
tate dissolved by boiling with water, no more soluble silver is 
contained in the ore, and the leaching is finished and can be 
stopped. It is important in the above test, to wash the pre¬ 
cipitate with water before dissolving the same in nitric acid, 
as Mr. Hoffman found that in the presence of alkaline hy- 
posulphides, only a partial precipitation takes place with 
chloride of sodium or none at all, if only small quantities of 
silver are dissolved in nitric acid. 

The time required for the extraction of silver, varies from 
8 to 20 hours, and depends upon the amount of silver con¬ 
tained in the ore, and the leaching capacity of the same. 
The silver from good filtering ore is more quickly extracted 
than from a slow filtering ore. 

Lumps formed in roasting, are not injurious. Mr. Hoff¬ 
man found that as long as they had a porous consistency, and 
provided the salt had been fixed in the ore before charging 
in the furnace, the extraction of silver was just as perfect as 
that from the fine part of the ore. It is, however, different 
if the lumps are very hard and clinker-like and have lost 
their absorbing power. 

For reasons given above, the tailings from the tanks, after 
a well conducted liviviation, will be found to be poorer than 
those obtained in the chlorination test of a sample taken from 
the furnace at the time of discharge. If a charge had been 
roasted to 85 or 87 per cent chlorination, the tailings of the 
vats will show that there had been an extraction from 87 to 
90 per cent of chloride of silver. The loss in weight which 
the ore sustains during leaching, has of course, to be brought 







fpoMT eUeV/\tio|^J 
o r 

LEACHING WORKS. 

JOiLTBY 

MALTER, LIND & ROGERS. 

SA NffodQff&frk- USA; 


plate: is 























































































































































































































































































































































































































CIRCULAR OF MALTER, LIND & ROGERS. 


47 


into consideration. This loss in weight depends on the nat¬ 
ure of the ore, and varies from 5 to 15, and more per cent, 
and consequently, a corresponding percentage should be de¬ 
ducted from the value of the vat tailings. 

After the silver leaching is concluded, the tailings left in 
the tank contain a considerable solution of hyposulphide of 
soda, which has to be displaced by water turned over on the 
tailing's. 

It was mentioned above that as soon as the solution showed 
signs of silver, the outlet hose is placed from the base metal 
through into the silver trough. The solution now runs into 
the distributing vat, thence by pulling out the first plug, it 
Rows into the first precipitation tank. If the first tank is 
filled to about 12 inches below the rim, the first plug is re¬ 
placed, and the second opened, and the solution made to fill 
the second tank, and so on. 

PRECIPITATION. 


As soon as one tank is filled with the silver solution, the 
operator commences with the precipitation. He opens slightly 
the clamp valve of the hose, which furnishes the supply of 
sulphide of calcium, and throws a little of the chemical on 
the solution, by moving the hose once or twice over the sur¬ 
face. This is done in order to see whether the solution is 
concentrated in silver or not, and serves as preliminary test. 
If the solution is found to be very rich, the hose is placed 
over the rim of the tank, the clamp valve opened wide, and 
a full stream of sulphide of calcium flows into the silver so¬ 
lution. At the same time, a vigorous stirring has to be main- 
tained. The full stream of sulphide of calcium is allowed to 
run in,till the scum formed by the stream becomes light yel¬ 
low. Then the valve is closed, but the stirring continued for 
a short time, when the precipitate is allowed to settle a few 
inches, and the second test is made by throwing some of the 
chemical, with the hose, on the surface. The clouds which 


form now, will be lighter in color and lighter in weight. A 
small stream of sulphide of calcium is now kept in, and the 
agitation continued till white clouds commence to appear, 
then the inflow of the chemical is stopped again, and after 
the precipitate has settled a few inches, the test with the 
sulphide of calcium is repeated. If no more colored clouds 
appear, the precipitation is finished, and after a good stirring 
the precipitate is allowed to settle to the bottom of the tank. 
By conducting the precipitation as described, the same can 
be performed much more quickly than by taking samples 
with a glass, and testing the solution outside the tank. It is 
well to make the check test after the main part of the silver 
has settled, and the solution become tolerable clear, by throw¬ 
ing a tumblerful of concentrated solution of silver over tin; 
surface flat. If it colors, it indicates a surplus of sulphide of 
calcium and solution has to be added until no more reaction 
takes place. 

The tank is left undisturbed until the silver solution is 
turned into the last precipitation tank, by which time all the 
precipitate has accumulated on the bottom, and the solution 
become perfectly clear, then it is drawn off by opening the 
the different outlet valves, with the exception of 
the lowest one. In case of need, this decanting can be done 
three-quarters of an hour after precipitation. As by the 
agit ation of the stirrer, considerable precipitate finds its way 
into the outlet hose, a bucketful of each has to be drawn off 
first before letting the solution run into the discharge trough 
which leads to the pump tank. The solution in the bucket 
contains precipitate, and is poured into the filters. By pre¬ 
cipitating the silver with sulphide of calcium the solution re¬ 
gains its solving property, and can be kept in constant use 
for quite a long time. Mr. Hoffman used the same solution 
which he prepared when starting the Silver King Leaching 
Works for more than a year and a half, at a production of 
nearly $3,000 in bullion per day. 





48 


CIRCULAR OF MALTER, LIND & ROGERS. 


The decanted solution flows into the pump tank, whence 
it is elevated by means of a pulsometeror any other suitable 
pump, to the reservoirs which are placed about ten feet above 
the ore tanks. 

TREATMENT OF THE PRECIPITATE. 


When enough precipitation has accumulated and the clear 
solution has been removed, the lowest outlet hose of the 
precipitation tank is placed either directly over the rim of 
one of the filters, or into a trough which leads to the filters, 
the clamp valve is opened and the contents of the tank well 
stirred. After the first filter is full the precipitate will flow 
into the next and so on until the whole charge is in the filters. 
This arrangement of filters is very convenient as it saves 
much handling of so valuable a substance, and does not re¬ 
quire much attention. In about three quarters of an hour 
the main part of the solution will have passed through the 
filter, leaving the precipitate in a muddy condition. The 
filters are now filled with hot water by means of a hose, and 
the precipitate well worked with a round pointed wooden 
spatula. The hot water passes through the filter still quicker 
than the solution. The precipitate is piled in the center of 
the filter in cone shape, and left to drain for two or three 
hours. 

At Melrose, the silver precipitate was drained ami dried 
in a centrifugal machine, with excellent results, in a very 
short time. A larger centrifugal had been made for the 
Silver King Mine, but the machine not having been well 
balanced, and the shaft being made too light, the use of the 
same had to be abandoned. So far, no further experiments 
have been made with the centrifugal, which, doubtless before 
long, will tike the place of the filters. 

Without previous drying or pressing, the precipitate is re¬ 
moved from the filters and charged into a small reverber¬ 
atory furnace where it is dried, and the major part of the 


sulphur burned off. Instead of a reverberatory furnace, re¬ 
torts can be used, and by distillation part of the sulphur re¬ 
gained. But this operation requires more fuel. If the burnt 
precipitate does not contain too much lead it will be part y 
covered with fine wires of metallic silver. 

In smaller works the precipitate is melted with iron and 
borax in crucibles, the products of which are bullion, matte 
and slag. The matte is very rich, and has to go back to 
the battery and is treated with the ore. The bullion is, 
according to the nature of the ore, and the more or less 
perfect roasting is from 800 to 975 fine. 

In larger works the crucible smelting is too tedious and 
expensive, and is the best performed with lead in a cupelling 
furnace. 

At the Silver King Mine, the precipitate was melted in a 
German cupelling furnace, in lots of 2000 to 3000 pounds, 
and obtained, after eight to ten hours, silver bullion 995 
fine, at a consumption of one to one and one-half cords of 
wood. The hearth was composed of a mixture of limerock 
and clay. The silver was dipped with ladles and poured into 
moulds. 

The ore of the silver King is very refractory, consisting of 
large quantities of rich zinc blende, antimonious fall 1-ore, 
peacock copper ore, galena, copper pyrites, iron pyrites, silver 
copper glance, and native silver. The latter was so promi¬ 
nent that almost half of the assay value of the ore was 
caused by native silver. The zinc blende is prominent The 
gangue consists of heavy spar, some quartz and porphyry. 
The poorer ore, with porphpry gangue was concentrated, and 
the concentrates mixed with the sparry ore and worked by 
lixiviation. The ore was roasted in a revolving furnace. 
During 1881 the mixture of ore and concentrates contained 
an average, according to 1100 assays, of $196.92; the aver¬ 
age chlorinatio \ during the same period, was 94 per cent, 
while the actual extraction amounted to 69.02 per cent. 








CIRCULAR OF MALTER. LIND & ROGERS. 


49 


There was a loss of <i per cent in the tailings, and of 4.8 per 
cent caused by roasting, dusting, and other sources of loss. 
During the same year 42,000 pounds of tine silver had been 
produced at a consumption of 43,148 pounds of sulphur, or 
about one pound of sulphur consumed to the pound of fine 
silver produced ; it takes twice this amount of lime. 

It' the ore contains gold, the silver bullion will always con¬ 
tain gold too. 

After a chloridizing roasting, some of the gold will be 
in the ore as sub-chloride, which does not dissolve in 
water, but does so in the solution, and is precipitated in the 
silver. If proper attention is paid, and the ore allowed to 
cool slowly after discharging from the furnace, much of the 
gold can be extracted by this process. From the concentra¬ 
tions of the Advance Mine, California, which contained 8250- 
in silver and 825 in gold per ton, by simple leaching, 85 
per cent of the gold was extracted. But such favorable 
results cannot be obtained from ores which are rich in 
gold and in which the value of the silver does not predomi¬ 
nate greatly. Auriferous silver ores can be successfully treated 
by this method. 

SULPHIDE OF CALCIUM. 


This chemical used as a precipitant for the silver, is 
prepared by boiling two parts of lime and one part of sul¬ 
phur with water ; if the lime is not of a good quality or not 
fresh, more lime has to be taken in proportion. The boiling 
is usually done in wooden tubs, by inserting steam, but it is 
not possible to keep them tight: as after a short time the 
chemical will find its way through joints and pores and keep 
dropping. Round tanks made of boiler iron 6 feet deep 
and 4 feet in diameter, are far better. Two tanks 
placed close together on a platform, in each is inserted a 
I' inch ? steam pipe extending to about 10 inches 
above the bottom. The bottom inside is covered with 2-inch 


planks to protect it from the poking with the stirring pole. 
Close to the wooden bottom each tank is provided with a 
4 inch discharge pipe which is closed with a wooden plug. 
These two discharge pipes project over a Hat wooden tank 
18 inches deep, and 8 feet in diameter which is provided with 
a filter bottom. In front, or to one side of this tank is placed 
a square tank 0' by O', by 2' deep so that the rim is lower than 
the bottom of the former tank. The square tank is also 
made of boiler iron, and serves to receive the manufactured 
solution of sulphide of calcium. An iron pipe leads down 
from it to the precipitation tanks. 

Water and lime are charged first into the boiler and steam 
turned on while the sulphur is sifted in when the water 
boils. The boiling has to continue during four hours ; then 
cold water is added to the liquid to cool it, and the sediment 
allowed to settle. The clear solution is drawn off by means 
of a syphon into the square iron tank ; the boiler is filled 
again with water: some more lime and sulphur added and 
another boiling made, after the clear solution of the second 
boiling has been drawn into the same tank as that for the 
first boiling, the sediment is discharged into the filtering tank; 
the filtrate of the sediment flows also into the square tank. 

A boiler tank of above dimensions may be charged with 
400 pounds of lime of good quality, then the tank is filled 
with water to about 12 inches below the rim, 200 pounds of 
sulphur added, and the whole boiled for four hours ; after 
the boiling is finished cold water is added to fill the tank to 
about 8 inches from the top. For the second boiling 70 
pounds of lime is taken, and 35 pounds of sulphur, and the 
same amount of water. In the first boiling is obtaine l a 
solution of 9 to 10°B, in the second, 7 to 8°B. 




50 


CIRCULAR OF MALTER, LIND & ROGERS. 


Concentration and Ore Dressing. 

There are many valuable mines the ores of which, in 
their natural state, are either too rebellious or low grade for 
successful and profitable reduction in the smelting furnace, 
the amalgamating mill, or in leaching works. These ores 
must first he subjected to the preparatory process of concen¬ 
trating and dressing. 

Concentration serves to separate the valuable metal con¬ 
tained in the ore, from part of its worthless gangue; dressing 
aims to separate the various components of an ore with a 
view of not only of reducing the bulk, but also of eliminat¬ 
ing such portions of the ore which may be injurious and 
detrimental to subsequent working. Thus for instance, many 
of our argentiferous galena ores carry zinc blende which is 
usually poor in silver and very injurious in the smelting fur¬ 
nace, because of its inclination to carry silver into the slag or 
out of the chimney, if volatilization occurs. Galena and 
zinc blende may be easily separated from each other in most 
cases by the ordinary methods of ore dressing, the former 
being much heavier than the latter, and of different crystal- 
ine structure, thus, loss of silver in smelting may be avoided 1 
and the zinc blende may be obtained by itself almost free 
from lead, in which state it can be utilized profitably for 
the preparation of zinc white. 

Among the ores which might be profitably prepared by 
dressing for subsequent working, are the following, the most 
common : 

1. Ores containing a large percentage of lead, especially 
carbonate of lead, clay, talc, or talcose slate, out of which 
the silver is to be extracted by amalgamation ; these sub¬ 
stances interfere with the amalgamation, causing loss of the 
precious metal. 

2 Silver ores containing antimony, cannot be well treated 
by the amalgamation process ; if roasted, volatilization is apt 
to carry off a large percentage of the silver, if amalgamated 


without roasting, the antimony wih probably enter the amal¬ 
gam making the quicksilver unfit to amalgamate with the 
silver, and thereby causing loss. 

3. Copper ores containing lead, arsenic, or iron (other 
than spathic iron). 

4. Tin ores containing iron, copper or arseno-pyrites, and 
zinc blende. 

5. All lead and copper ores which are to be smelted, and 
the gangue of which does not make a favorable slag without 
expensive fluxing. 

6. Auriferous pyrites containing talc, if the gold is to be 
extracted by the chlorination process, talc absorbs the chlor¬ 
ine gas; roasting the oie with much salt might overcome the 
difficulty ; it might also cause loss of gold in roasting. 

The desirability of preparing ores by concentrating or 
dressing for the extraction of the precious metal, is purely an 
economic question. If the preparation of the ore costs more 
than the saving effected in its final reduction, then such 
preparation would not be'desirable. 

The question of desirability of concentrating or dressing 
an ore, is easily determined in any particular case, if the 
cost of concentration is known. For the purpose of deter¬ 
mining this question, the cost of the dressing may be roughly 
set down at from 50 cents to one dollar per ton of ore, tie- 
pending on hardness of the ore, cost of fuel and labor. 

The feasibility of the concentrating or dressing ore depends 
upon the specific gravity of its components upon its crystal- 
ine structure, and its chemical combination; it cannot be de¬ 
termined in any other way than by experiment; the sample 
to be experimented on should be large, and should be care¬ 
fully taken from the mine, to represent a true average char¬ 
acter of ore to be worked. 

The ores best suited for concentration or dressing are those 
in which the various metals form separate crystals of favor¬ 
able shape and size, and differing widely in specific gravity 



































































































































































































































































































CONCENTRATION WORKS 

OF 

TWO HUNDRED TONS DAILY CAPACITY. 


Plate 19 

Shows the side elevation of Two Hundred-Ton Concen¬ 
trating Works for treating silver ores, which we have lately 
constructed for the Silver Queen Mining Company at Los 
Bronces, Sonora, Mexico. The ore is crushed first in large 
or coarse Rock-breakers, and after passing through the 
washing and hand-picking process, it is re-crushed in fine 
Breakers and coarse crushing Rolls, and separated in var¬ 
ious sizes by screening. After sizing it by revolving screens, 
provided for the purpose, thecoarser portions are again passed 
through fine crushing Rolls to be re-crushed and then re¬ 
sized. The various sizes of ore pass to the jigs, and from 
them to the Tailing Separators described on page 23. The 
Tailing Separators supply the slime jigs and percussion 
tables, which completes the operation in this Mill. The 
concentrates are leached in separate works to obtain the 
precious metals. 



CIRCULAR OF MAI 


among themselves and with their gangue. Of course, metals 
which are in alloy with each other cannot be separated by 
dressing. 

Ores containing iron, copper, or arsenical pyrites are easily 
concentrated in most cases; gray copper, brittle and ruby 
silver and sulphides of silver, as contained in most ores, are 
less easily separated. 

Decomposed ores are apt to be reduced largely to so-called 
slimes during process of reduction, and for that reason are 
often unsuited for concentration. 

The following is a table of the specific gravity of various 
metals and components of ore: 

SPECIFIC GRAVITY OF METALS AND MINERALS. 


METALS. 

Gold.19.25 

Mercury.13.26 

Lead.11.35 

Silver.10.45 

Copper. 8.89 

Iron. 7.78 

Tin. 7.30 

Zinc.. 7. 

SPECIFIC GRAVITY OF MINERALS ASSOCIATED 

WITH ORES. 


Hornblende.2.8 to 3.2 

Syenite.2.7 to 3. 

Trap or Basalt.2.8 to 3.2 

Porpoerytrachyte or Felspar.2.3 to 2.7 

Granite or Gneiss.2.4 to 2.7 

Micaceous Slate.2.6 to 2.9 

Clayey Slate.2.6 

Limestone and Dolomite.2.5 to 2.9 

Sand Stone. ..2.4 to 2.7 


ER, LIND & ROGERS. 


51 


COMPARATIVE HARDNESS AND SPECIFIC 
GRAVITY OF ORES. 


LEAD. 

HARDNESS. 

SPECIFIC O 

KAVITY. 

Galena (sulphide of lead) 

2.5 to 2.75 

7.5 to 7.6 

Sulphate of lead 

2.3 to 2.7 

6.25 

to 6.2!* 

Carbonate (white) 

3.- to 3.5 

6.45 

to 6.48 

Phosphate (green or brown) 

3.5 to 4.10 

6.58 

to 7.04 

Chromate (bright and red) 

2 5 to 3. 

6. 

to 6.04 

Molybdate 

2.7 to 3. 

6. 

to 6.8 

Oxide of Tin 

6. to 7. 

6.5 

to 7. 

Tin Pyrites 

3. to 4. 

4.79 

to 5. 

COPPER. 




Sulphide of Copper 

2.5 to 3. 

5.5 

to 5.8 

Oxide 

3.5 to 4. 

5.9 

to 6. 

Carbonate 

3.5 to 4. 

4. 

to 4.1 

Sul jib ate 

2.2 

2.21 


Silico Carbonate 

2.3 

2. 

to 2.2 

ZINC. 




Red Oxide of Zinc 

4. to 4.5 

5.43 

to 5.52 

Sulphide 

3.5 to 4. 

4.02 

to 4.07 

Carbonate 

.). 

4.33 

to 4.44 

Silicate 


3.43 


ANTIMONY. 




Sulphide of Antimony 

2 

4.51 

to 4.62 

Jamesonite 

2 

5,5 

to 5.8 


























52 


CIRCULAR OF » 


The concentration and dressing of ores requires a large 
amount of water. Dry concentration has not proved suc¬ 
cessful for the reason that air is too light a medium, while, 
because of its lightness it does theoretically seem better 
suited than water, being more sensitive to slighter differences 
of specific gravity, it practically causes insurmountable 
difficulties; being light, it requires great motion to give the 
particles of ore to be concentrated, the necessary activity for 
separation, especially in the operation of jigging, thereby 
largely increasing the attrition, percentage of dust, and con¬ 
sequent loss of metal. In the heavier medium of water the 
attrition of the ore is a minimum, its particles being kept 
almost afloat. 

The percentage of value obtained or obtainable in the 
concentrates depends largely upon the character of the ore, 
upon the proper construction of the machinery employed 
arid upon its proper manipulation. The closer the valuable 
metal in the ore is concentrated, the greater the loss 
resulting from the operation. 

Ores, the metallic portion of which is very soft, or the 
metal of which is finely disseminated through the gangue, 
are not easily concentrated to a high percentage, since, in 
the process of crushing, the metals they contain are apt to 
be reduced to a very fine powder that may remain suspended 
in water for a great length of time, forming so-called slimes, 
which do not readily yield their value, and are usually run 
off as tailings; sometimes they are o-athered in reservoirs 
where the metal they contain is given time to settle, and the 
clear water alone is permitted to run off or pumped back 
to serve again in the process of concentration. An efficient 
way of working slimes is the pan amalgamation process, if 
the pans are properly constructed, and the ore be suitable 
for amalgamation. 


LIND k ROGERS 


The dressing of ores may be analyzed into the following 
distinct manipulations: 

1. Hand picking. 

2. Washing of ores. 

3. Coarse and fine crushing in breakers, rolls and stamp 
batteries. 

4. Sizing of crushed ore according to both diameter and 

o o 

shape. 

5. Jie’oing. 

•-5o O 

6. Working of fine ores upon inclined planes. 

7. Working of slimes. 

HAND PICKING. 


The separation of the solid pieces of metal from the ore 
containing both metal and gangue, may, to some extent, be 
effected by hand picking before the ore is crushed. Such 
separation when possible, is desirable, as it saves unnecessary 
crushing, and lowers the consequent loss by sliming and con¬ 
centrating. 

The ore may be hand picked two or three times, first as it 
comes from the mine, and second, as it comes from the 
coarse breaker, and third, as it comes from the washing 
machine. 








EixEVAXi □ N 

THREE HUNDRED TON 

CONCENTRATION PlsANT. 

ioitr sr 

MALTER, LIND RDBER5. 

Jav frai?^o, foil. 

ufH.^^roN & ixEY, <>/ 


PLATE 20, 


































































































































































CONCENTRATION WORKS 

OF 

THREE HUNDRED TONS DAILY CAPACITY. 


Plate 20 

Gives a side elevation of Three Hundred-Ton Concentra¬ 
tion Plant, which we are now constructing for La Trinidad 
Mining Company at Trinidad, Sonora, Mexico. The opera¬ 
tions in this Mill are, in a great measure, similar to the Sil¬ 
ver Queen. The concentrates are roasted and smelted in 
separate works, provided for that purpose. 


TRANSMISSION OF POWER BY BELT. 


Each inch of width of a good leather belt, traveling with 
a speed of 1000 feet per minute, will transmit one horse 
power. Royers’ pulled rawhide belting is capable of trans¬ 
mitting 35 per cent more power than first-class oak-tanned 
leather belting, and 45 per cent more power than good rub¬ 
ber belting. In wet places rubber belts will wear best, in 
dry places the pulled rawhide will outlast all others. 





CIRCULAR OF MALTER, LIND k ROGERS. 


53 


WASHING OF ORES. 

The washing of ores is effected either in sluices, or upon 
revolving tables, or in revolving drums. 

Our patented construction of an ore washing-machine of 
the latter description, is illustrated in the accompanying en¬ 
graving. It serves two purposes, 
first, to clean the ore so that the 
solid pieces of metal may be easily 
distinguished by the pickers from 
the impure ore, and second, to sepa¬ 
rate the various sizes of ore so as 
to avoid unnecessary crushing and 
consequent sliming of the ore. We 
make these machines with single 
or double cone. The double cone 
machines separates the ore into 
more sizes than those with single 
cones. 

The machine illustrated consists 
of a single revolving cone of perfo¬ 
rated plate, which is set upon a tank, 
and is partly submerged in water. 

The ore is introduced into the 
smaller end of the cone as it comes 
from a coarse breaker. The finer 
portion passes through the perfo¬ 
rations of the cone into the funnel 
sizer of the tank below, which sep¬ 
arates the waste slimes from the ore 
to be passed to the jigs and tables. 

The coarse ore which does not pass 
through the holes of the sereen, but 
passes to the larger end of the 
cone and is then thrown out bv 


means of elevator cups, upon an inclined plane, where 
it may again be hand picked before being passed to the 
finer crusher or rolls. 


Cut 27—Ore Washing Machines. 






















































































































CIRCULAR OF MALTER, LIND & ROGERS. 


54 


CRUSHING OF ORE 


FOR CONCENTRATION. 


In crushing- ores for concentration, great care must be 
taken not to reduce any considerable portion of it to a de¬ 
gree of fineness greater than required for separation of the 
components of the ore, and for concentration. All unneces¬ 
sary crushing or handling, causing attrition, makes slimes 
and results in loss. 

All machines designed for the crushing of ore to be con¬ 
centrated, must be so constructed as to avoid all unnecessary 
grinding of the ore. 

Machines which crush the ore by pressure are preferable 
to those which crush it by blow or grinding motion. 

Properly constructed rock breakers make less slime than 
rigid rods; rigid rolls make less than cornish spring rolls: 
and these again make less than stamp batteries. 

lo avoid sliming, it is necessary to employ rock breakers 
to crush the ore before passing it to the rolls or stamp bat¬ 
ten . hirst, coarse breakers which reduce the ore to the size 
of a hen’s egg and smaller, and then fine crushers to reduce 
it to the size of walnuts, and less. 

It is also desirable to screen the ore after every operation 
of crushing, in order to prevent the ore already fine enough, 
from passing again through a crushing machine and subject¬ 
ing it to more attrition that causes slimin'--. 

COARSE BREAKERS. 


As coarse breakers, we employ the Blake Rock Crusher of 
improved pattern, as shown on this page and the next. 



Cut 28—Improved Blake Crusher. 






























































IMPROVED 

BLAKE ROCK BREAKERS 



These crushers are the most commonly used for coarse crushing 
of ore when large quantities are to be prepared for the stamp 



















































































































































































































56 


CIRCULAR OF MALTER, LIND & ROGERS 




This crusher lias the advantage of simplicity and adjusti- 
bility, or stroke, which makes it suitable for ores of varying 
characteristics. 


I 























































\ t- i « 




W 



E 

O 


rr 

ca 


COMPOUND PUMPIN6 ENGINES 

beSiGI'JEb BY 

MAL.TER. kIND « ROGERS. 

?aH 

































































































































































































































































































































































































. 

. 

' 



. 









CIRCULAR OF MA 


The crushing power is more directly applied than in any 
other breaker, thereby the number of wearing parts are 
greatly decreased. A breaking cup B with a rubber block 
R is interjoined between the toggle and the jaw of the 
breaker to prevent any serious breakage of the machine, 
which sometimes occurs when pieces of steel sledges or gads 
get between the jaws of the breaker. 

Cut 33 shows the shaft of the breaker with the toggle 
and eccentric. All the wearing surfaces are large so as to 
reduce the wear to a minimum. 



Cut 33- Toggle with Eccentrics, to Adjust the Discharge. 

FINE BREAKERS. 


As fine breakers, we employ the Champion Ore Crusher, 
which is shown in the accompanying plate. 

It has two peculiar features : 

1. Its jaw has its minimum motion below, at the dis¬ 
charge ; by this means it becomes possible to crush the ore 
uniformly finer than in the other breakers. 

2. Its discharge opening is easily adjustable by means of 
an eccentric, which is operated by the lever M, so that when 
the jaw plates wear the discharge opening may still be kept 
of the original and uniform size. 

A breaking cup R, is placed between the moving shaft and 
the movable jaw, to prevent disastrous breakage of the frame, 
which sometimes occurs. We use patent steel jaws in 
either of these breakers, or we make the jaws, as shown in 
cut, of cast or wrought iron or of steel. Tempered steel bars 
are firmly inserted into it. All the workmanship and 
material of these crushers is the best of their kind. 


tR. LIND &r ROGERS. 




Outs 34, 35, 30 




JAW PLATE 

—WITH— 

Steel Bars. 


Champion Breaker for Fine Crushing of Ore, 





















































































58 


CIRCULAR OF 


ROLLS FOR CRUSHING ORE. 


Cut 38 illustrates Malter’s patent rolls, for which we 
claim superiority over other rolls in use, on ground of 
the following points: 

1. They are more substantial. 

2. The gears being placed directly over the pinion, do not 
require long teeth or constant adjustment, as do all other 
geared rolls, to accomodate the motion of the movable 
roll, or the wear of the shell. 

3. The shells of the rolls are easily removed without dis¬ 
turbing the gears. 

4. Roth shells may be turned oh' at once in case of wear. 

5. The rolls are so guided by means of a wrought-iron 
frame that they cannot twist as they are thrown apart, thus 
all danger - of breakage of gears is avoided. 

6. If used as rigid rolls for line crushing, the distance be¬ 
tween the rolls, and thereby the size of the grains required, 
is easily adjusted by means of the breaking cup. 

7. The same set of rolls may be used as rigid or movable 
rolls, by making but the slight change of exchanging the 
breaking cup for springs. 

We make the shell of the best material; we bore them 
out so as to lit true on a tapering cone. The roll shafts we 
make of best hammered iron or steel. 

Coarse crushing or so-called roughing rolls should be used 
with a movable roll held in place by a suitable spring, and 
they should be driven by gears. 

Fine crushing or finishing rolls should be used as rigid 
rolls to prevent making slimes, and are better driven by a 
large belt-wheel direct, without the use of gears. 


LIND & ROGERS. 


When the metal of the ore to be concentrated is finely dis¬ 
seminated through the ore, it is often advantageous to crush 
the ore, or at least the “seconds” from jigs, in a stamp bat¬ 
tery. To avoid sliming as much as possible in such cases, a 
water-box should be attached to the outside of mortar in 
such a manner as to submerge the screen entirely in water, 
and thereby prevent the clogging of the screen, which in¬ 
creases the percentage of slimes materially. An arrange¬ 
ment of this description is illustrated on page 7. 

Another effective method to prevent sliming, is that of 
crushing over the edge of a board into water-boxes outside 
the mortar, which, in such cases, serves as sizer, and does 
the duty of a pointed box or spitz-rasten. 

The more water run through the moisture while crushing 
the sooner will the fine ore be discharged and the less slimes 
will result. 

On the following pages we show cuts of our patented 
constructions of coarse and fine crushing rolls, such as we 
build for use in concentration plants. 











\f\rvr\ 


CIRCULAR OF MALTER, LIND & ROGERS. 


59 




Ground Plan of Coarse Crushing- Rolls 


























































































































































































































































































































































































































60 


CIRCULAR OF MALTER, LIND & ROGERS, 





Cut 39 -Sectional View, of Malter’s Rigid 

Crushing. 


for Fine 



Cut 40-End View of Geared Rolls. 




Rolls 












































































































































































































CIRCULAR OF MALTER, LIND & ROGERS. 


in 



In wet concentration plants the stuff produced by 
crushing in rock-breakers and coarse-rolls is separated by re¬ 
volving receiving drums, through the screens of which the 
finer material passes by chutes, directly to the sizing screens, 
while that which is too coarse to pass is returned by ele¬ 
vators to fine crushing rolls. Cuts 39 and 40 show Matter’s 
rigid rolls for re-crushing of ore, and cut 41 illustrates 
spring rolls for fine crushing. 

The sizing screens separate again the sands and slimes 
from the coarse material, and carry them to the spitzkasten 
or hydraulic separators, which in turn feed the percussion 
tables or concentrators. The coarse material from the sizing 
screens is distributed to the jigs. The size of this stuff ranges 
from an eighth to a thirty-second of an inch in diametei, 
and sometimes in lead and copper works larger, and in silver 
mills smaller. The jigs are provided with flat steel bars 
to receive wire-screens having meshes corresponding to the 
size of the material to be treated, also to the sizing screens 
feeding the jig. 

The jigs constructed by us, are continuous working, that is, 
they are fed continuously by the sizing screens, and are also 
self-discharging. The separation of the metal and gangue 
in the jigs is effected by water actuated by plungers or pis¬ 
tons, worked from horizontal shafts by eccentrics and rods 
forcing the water up through the screens, lifting the ore par¬ 
ticles deposited upon them. 







































































02 


CIRCULAR OF MALTER, LIND & ROGERS 


By this means, the material is lifted and dropped, 
varying in speed or number of strokes from eighty to one 
hundred and fifty,according to the fineness of material treated, 
the heavier metals reaching the screens first, while the lighter 
gangue remains on top, and is gradually worked along from 
one screen to another, until it is finally discharged from the 
waste gate, located at the opposite end of the jig frame from 
which it enters, while the metal and valuable stuff partly 
passes through the screen or is discharged from gates in front 
into the receiving boxes underneath, and from them carried 
away in cars for further treatment—roasting, smelting, 
leaching, etc., as each case may require. 

The material coming to the jigs, in which metal and 
gangue are yet mixed in the grains, and which therefore 
cannot be separated by jigging, but requires to be re-crushed, 
pass through side gates to rolls provided for that purpose. 

All the operations can be regulated so that practically 
nothing but pure waste is discharged, and only the val¬ 
uable metals saved, providing always, that the jigs are 
properly managed and the screens are selected to suit the 
ores to be treated. 

We also construct jigs for treating fine stuff which is 
commonly worked with the slimes on tables. The success¬ 
ful operation of the jigs depends very largely upon the 
ability of the operator to adjust them to the work. 

SIZING SCREENS. 


The sizing screens we generally build cylindrical in shape, 
with convenient devices for securing and removing the 
screens when necessary ; they are driven either directly by 
belts from counter shafts, or by bevel and spur gearingwhen 
worked in sets from one driver. The carrying shafts are 
preferably made of tubing with solid journals and double 
adjustable bearings. 


Each screen is provided with sheetiron receiving aprons* 
which supply the succeeding screen ; spouts are also ar¬ 
ranged to deliver the proper material to the jigs. These 
screens are made of sheetiron punched with numerous 
holes to correspond to the jigs which they serve. 

In the work of concentration the very fine sands and 
slimes are conducted by spouts from the sizing screens to 
the hydraulic separators which feed the slime jigs and 
tables (see page 24). 

These separators are arranged in sets of three or more, 
depending upon the characters of ore treated. If much 
slime is to be handled then more and larger separators 
must be used. These separators or pointed boxes operate 
upon the principle that the finer the sands the greater the 
water surface and the slower the motion needed to settle it, 
therefore, in operating, the coarsest sands are collected in 
the smallest separators, the current being so rapid that only 
the heaviest particles sink while the rest overflows into the 
next larger tank, where the same quantity of water flowing 
in, spreads over more surface, and the next size is settled, 
and soon to the end of the system, when the last overflow 
carries away the slime waste and surplus water. In some 
locations where the necessary water is scarce the last overflow, 
when settled and clean, is pumped back to be used again, 
though this not desirable if it can be advoided. 

The sands collected in the separators are fed continuously 
to the slime jigs and tables where both are used, and the en¬ 
tire plant is thus continuously working and as nearty as 
posssible automatic in all its departments, from the delivery 
of the ore in the ore-house, to the concentration of the 
slimes, each set of machines depending for its supply upon 
the next above. 







CIRCULAR OF 


In distributing the slimes and sands upon the percussion 
tables or other concentrators, it is necessary to have the stuff 
sufficiently diluted so that it can be spread evenly over the 
tables near the top of the incline, in a thin sheet, so that the 
work of the table can better act upon the particles; clean 
water is also introduced upon the table, which tends to wash 
away the mineral sands and the gangue, but the metallic 
portions being heavier, resist the action of this water more 
than the gangue, a partial separation is thus effected, which 
is more fully accomplished by the quick jarring motion 
which the table receives by means of cams acting against 
springs, and operated by pulleys and belts from counter¬ 
shafts, or by other contrivances, giving the whole table a 
side-wise or end motion, which is partly arrested by striking 
against percussion blocks. 

The tendency of the material upon tables is to form 
lines of descent more or less curved; the lighter por¬ 
tions generally nearly straight, and the heavier metallic por¬ 
tions in curved lines; three lines are formed—one of pure 
metal, one of pure waste or gangue, and one of mixed metal 
and waste, if rich enough, is worked over again on the same 
table, or upon tables located beneath, to receive the material 
from the tables above, or if the middling stuff* is not valuable 
enough to be worked separately, it is either mixed with 
the pure metal, or allowed to follow the waste. 


., LIND & ROGERS. 


(13 


The character of the surface of the table and the incline 
given to it have much to do with the work done; the 
greater tjie incline the less clear water is used, and the re¬ 
verse. The construction and adjustment of these tables is 
an important feature in the successful working of slimes, 
With properly constructed table the loss in working sands 
or slimes is very trifling, a high percentage of the value 
of the slimes can be saved, varying with the character of 
the ore. 

Belt concentrators, such as the Frueor Triumph Machines, 
are also used for concentrators of slimes. 

The relative value of these different styles of concentrators 
depends upon the class of work to be done ; for gold sul- 
phurets, the endless belt machines, like the Frue and Tri¬ 
umph, are mostly used at present; this arises from the fact, 
that the percussion table proper, has never been practically 
introduced for this purpose. 

In works designed for concentrating silver ores which 

O O m 

easily slime the percussion table is by far the most efficient 
machine; and since the concentration of sliming silver ores 
is far more difficult than the concentration of iron pyrites 
from gold-bearing quartz ores, it would seem reasonable 
that a percussion table properly constructed for the purpose 
would also be more effective for saving gold sulphurets. 









64 


CIRCULAR OF 



Cut 42—Improved Combination Pan. 


, LIND k ROGERS. 


PAN AMALGAMATION. 


The process of extracting gold and silver from their ores 
by pan amalgamation is a California invention. 

Since it came into use the amalgamating pan has 
undergone very many material changes. The main features 
of its improvements consists in bringing the ore to be amal¬ 
gamated more effectually in contact with the mercury, 
thereby increasing the efficiency of the apparatus and 
shortening and cheapening the process. 

COMBINATION PAN. 

Cut 42 shows the combination pan which is still exten¬ 
sively used in silver mills. It is generally 5 feet in diame¬ 
ter and 3 feet in depth ; its sides are made of wood when 
the ore to be worked in them has previously been subjected 
to a chlordizing roasting, otherwise they are more usually 
made of cast iron, occasionally, also, of wrought iron. 

Underneath the pan bottom there is a steam chamber, into 
which the exhaust steam from the engine is usually intro¬ 
duced for the purpose of heating the ore pulp and mercury. 

The inside of the pan bottom is covered. by dies made 
either in sections or in a solid ring. The pan muller with 
its shoes entirely covers the dies. The space between the 
dies and their outer and inner periphery are usually tilled 
with wood or cement so as to preserve a smooth surface 
over the entire bottom of the pan. 

The center of the pan bottom rises in the form of a high 
cone, the upper part of which serves to hold the upright 
shaft or pan spindle, that transmits the power and revolv¬ 
ing motion by means of a driver to the pan muller, revolving 
it in a horizontal plane above the pan bottom or dies. 


































































































































































CIRCULAR OF 


The distance between the shoes and dies may be adjusted 
by means of screws and hand wheels bearing at the upper 
end of the spindle. 

The pan may be used either for the purpose of grinding 
or amalgamating. 

When the pan is used for the purpose of grinding the ore 
pulp, the screw is raised and the muller with its shoes is 
thereby lowered so that its weight rests upon the dies. 
\\ hen the pan is used as an amalgamator then the muller 
and shoes are raised from f to 1 inch above the dies. 

In this construction of the pan, the muller plate covers 
the entire surface of the dies and the arms of the muller 
are attached to the inner periphery of the muller plate. 
When in motion the arms and muller plate virtually forms 
a partition between the bottom of the pan upon which the 
heavy mercury used in the amalgamating of ore gathers 
and the upper portion of the pan which holds the lighter 
ore pulp. To bring about a thorough mixture of the two, 
the muller is made to revolve very rapidly—65 or 70 revo¬ 
lutions per minute—thereb} T the mercury beneath the pan 
shoes is divided or shattered in small globules, which are 
forced upward into the ore pulp and float in it if the pulp 
be sufficiently stiff. 


,, LIND & ROGERS. 


65 



Cut 43—Standard Pan. 




























































































66 


CIRCULAR OF 



STANDARD PAN. 


Cut 43 and 44 shows an amalgamating pan of a later con¬ 
struction, first introduced by us in the mills about Tombstone. 
It differs from the former in having a narrower muller, 
the shoes projecting from 5 to 6 inches beyond either edge 
of the muller. 

The object of narrowing the muller is to bring the 
ore to be amalgamated more effectually into contact with 
the mercury, which being heavy, generally gathers at the 
bottom of the pans. As the muller revolves the beveled 
edges of the shoes attached to it force the pulp through the 
spaces between them in a downward direction into the 
mercurv, which is thereby made to take off the revolving 
motion of 
muller and 
pulp, and is 
more read¬ 
ily mixed 
with latter 
than in the 
former con¬ 
struction of 
pan, hence 
the motion 
of the mul¬ 
ler need not 
be rapid nor 
the ore pulp 
so thick to 
effect the 
same result. 


Out 44—Ground Plan of Standard Pan. 


, LIND & ROGERS. 


SETTLER. 


The engraving on page 67 represents a sectional view 
and ground plan of a settler as commonly used in silver 
mills, for the separation of the amalgam and mercury from 
the ore pulp as it comes from the pans. 

It is an open vessel, the bottom being of cast iron, sides 
of wrought iron or wood, from 8 to 9 feet in diameter, sides 
from 3 to 4 feet high. An upright shaft, which receives its 
motive power through the gear wheels, transmits a rotary 
motion to a muller-plate or arms carrying wooden or iron 
shoes. 

The ore pulp coming from the pans is greatly diluted in 
the settler to facilitate the separation of the heavier portion, 
which contains the amalgam and mercury and which sinks to 
the bottom from the lighter sands, which pass out through 
holes in the sides of settler into the waste sluices or the 
funnel separators. 

The mercury and amalgam gather in a bowl attached 
to the outside of settler near its bottom. 

Dashboards are commonly suspended in the pulp as 
shown in the sectional view of settler, for the purpose of 
deflecting the circulating sands toward the bottom of 
settler and thereby facilitate the separation. 

The settler is a continuous working machine, although 

c? * O 

the pulp from the pans is not always continuously charged 
into it. 

One settler generally serves two pans; only in excep¬ 
tional cases is it necessary to employ a settler for each pan. 
In some cases one settler may be sufficient to separate the 
ore pulp coming from three or more pans, as in the contin¬ 
uous charge mill and others. In gold mills with our contin¬ 
uous-pan amalgamation process the settler may be entirely 
dispensed with, the continuous-working separators taking 
its place. 
























SCHMIDT & CO. 


CIRCULAR OF MALTER, LINI) & ROGERS. 


07 





























































































































































CIRCULAR OF MALTER, LIND & ROGERS. 




Cut 44. 


Retorts for Silver Amalgam. 


Cut 45. 







































































































































































































CIRCULAR OF MALTER. LIND & ROGERS. 


60 


AMALGAMATION OF GOLD IN THE STAMP 
MORTAR AND IN THE PAN. 


The gold contained in the quartz as found in our mines 
is usually separated from its matrix by amalgamation in 
the stamp batteiy and upon copper plates coated with 
mercury, which are placed in the bottom of the sluices that 
carry away the tailings. 

Very pure and coarse gold can be readily amalgamated 
in this manner, although the percentage of loss in this 
primitive process of mortar and plate amalgamation is al¬ 
ways great, far greater than the majority of millmen are 
inclined to admit. But when the gold is not pure and 
coarse, for instance is rusty, covered with oxides of iron or 
copper from decomposed pyrites, or is very finely divided 
through the quartz, or is in alloy with some silver, as is very 
frequently the case, then the battery amalgamation is not 
usually found to give satisfactory results. Mines con¬ 
taining such ores are very frequently condemned as 
worthless when the customary treatment of the ore by 
mortar amalgamation fails to yield a profitable result. 
More effective methods of amalgamation are but little 
known and but rarely resorted to. Thus, for instance, 
the mines at Bodie, Cal., were, shortly after their discovery, 
abandoned for the reason that the ordinary amalgamation 
process in the mortar, or pan, failed to extract the gold, 
which is very fine, and in alloy with some silver. It was 
ten years after their abandonment that a somewhat im¬ 
proved pan-amalgamation process was introduced by us, at 
the Standard mine, Bodie, which proved successful and 
turned the deserted camp into one of the most prosperous 
mining districts of this coast. 

Clean and pure metallic gold, if not so fine and slimy as 
to float on the water, unites very rapidly with even cold 
mercury upon mere contact with it; but fine, slimy or rusty 


gold, or gold in alloy with silver, will not readily amalgam¬ 
ate with mercury, hence more efficient means than the 
slight, uncertain and inefficient contact with cold mercury 
in the mortar or upon mercury-coated copper plates must 
be employed to amalgamate gold that occurs under such 
conditions. 

Mr. Raymond, United States Commissioner of Mining- 
Statistics, has treated the important subject of gold and 
silver amalgamation in his official reports. He has clearly 
shown the wastefulness of the crude mortar amalgamation 
process in all cases ; he asserts and proves that as much as 
50 to 60 per cent, of the value of gold-bearing quartz are 
usually lost in stamp-mills which are considered to work 
successfully. 

The great loss of precious metal may be principally at¬ 
tributed to the following causes : 

1st—The mercury in the mortar and plate amalgamation 
cannot be heated, and quicksilver when cold is far less 
efficient in its power to dissolve precious metals than it is 
when heated to about the boiling point of water. If hot 
water were used in the stamp mortar for the purpose of 
warming the mercury the latter would not adhere to the 
amalgamation plates. 

2d—The mercury which is placed into the mortar stays 
largely at the bottom and does not come into favorable 
contact with the ore to effect the amalgamation of the 
metal. 

The amalgamating plates which are placed outside of 
the mortar, and which are intended to catch the amalgam 
and float gold that escape from it, do not usually answer 
their purpose with much efficiency ; they do not present the 
most favorable condition under which amalgamation can 
take place. The constant current of water flowing over 
them carries much of the amalgam away with it as also gold, 
especially when they are new and but thinly coated with 









70 


CIRCULAR OF MALTER, LIND & ROGERS. 


mercury the copper is apt to oxidize and become covered 
with a greenish coating which quite prevents the adhesion 
of the floating amalgam to it. 

3d—It is impossible to put the mercury in the best con¬ 
dition to unite with the precious metal, first for the reason 
that confined in the mortar it is not accessible to the inspec¬ 
tion of the amalgamator, and secondly, if cyanide of pot- 
tassium or sodium amalgam or other re-agents that may be 
needed to preserve the amalgamating power of the mercury 
be added, their power would be largely lost in the great 
currents of water that flow through the mortar. If clean 
gold-bearing quartz is worked, the mercury in the mortar 
is not apt to get foul speedily ; but if impure ores are to be 
treated in the stamp mortar then the quicksilver may lose 
its capacity to unite with the metal. 

4th—The attrition of the sands consequent to the action 
of the stamp is apt to “flour” the mercuiy and amalgam, 
causing it to be carried away with the water. 

Of floured metals, Mr. Raymond says: “ Flour or granu¬ 
lated quicksilver and fine particles of gold have, in common 
with some other polished metals, the property of condensing 
on their surfaces films of air which practically decrease the 
specific gravity of the particle and cause it to float in the 
water or upon its surface, whereby serious loss of precious 
metal is occasioned. 

AMALGAMATION OF GOLD IN PANS. 

The ordinary pan-amalgamation process overcomes the first 
but not the three last of the above-mentioned defects in 
mortar amalgamation, and hence the ordinary pan process 
does not usually prove efficient where mortar amalgam¬ 
ation fails. Moreover, the cost of the ordinary pan amal- 
ation is fully 50 per cent, higher than that of the mortar 
amalgamation, and the first cost of the plant twice as great. 


MALTER’S CONTINUOUS-PAN AMALGAMATION 

PROCESS. 

For the working- of gold and silver ores which are difficult 
to amalgamate by the ordinary battery and pan amalgam¬ 
ating process, we have designed and patented an improved 
method of continuous-pan amalgamation, which success¬ 
fully overcomes 
the difficulties 
stated above. 

It differs 
mainly from the 
ordinary meth¬ 
ods of contin¬ 
uous or other 
pan amalgam¬ 
ation in the con¬ 
struction of the 
pan and in the 
substitution of 
our patent tail¬ 
ing separators 
for the custom¬ 
ary settler and 
in the method of 
using the mer¬ 
cury in the pan. 

Plates 7 and 
13 show plans 
of such im¬ 
proved gold and 
silver amalgam¬ 
ating mills. 

Cut 49 shows 
a sectional view 

Cut 49-Matter’s Patent Amalgamating- Pan. 




































































CIRCULAR OF MALTER, LIND & ROGERS. 


71 


and plan of the 
Malter pan. It 
differs princi¬ 
pally in four es¬ 
sential features 
from the latest 
improved Com¬ 
bination 0 1 - 
Standard pan. 

1st—Themul- 
ler arms of the 
pan form a 
basket which is 
encircled by a 
copper or a 
wrought -iron 
ring. This ring- 
divides the pan into two compartments, the outer and 
inner compartment, and effects a thorough circulation of the 
pulp in the pan and its mixture with the mercury without 
the use of the inefficent dashboards. 

2d—A quicksilver bowl is attached to the side of the pan. 

3d—No muller plate or iron shoes or dies are used. 

4th—The motion of the muller or rings is geared to run 
slowly. 

If gold or a metallic silver are to be amalgated, the ring 
of the muller is made of copper and coated with mercury. 
If chlorides of silver are to be treated, a wrought-iron ring 
may be added. In either case the ring can easily be removed 
by merely lifting it out of the pan. In its use this pan 
differs from the combination pan— 

1st—In the manner of application of mercury to the ore 
pulp. 

2d—In the circulation of the pulp, and 

3d—In the treatment of the mercury. 


APPLICATION OF THE MERCURY TO THE ORE. 

1st—The mercury is charged into the pan and remains 
largely at its bottom, in a contiguous body though, and over 
which the pre-pulp is made to pass continually. 

The amalgating ring extends to nearly the surface of the 
ore-pulp, and serves to catch the particles of metal in the 
pulp; it revolves with the muller and ore-pulp, and its 
amalgamating surface is constantly piesented to the pulp 
under the most favorable conditions for the adherence of 
the precious metal to it. When enough amalgam has at¬ 
tached itself to the surface of the ring, it is removed to be 
scraped off and another ring is put in its place. 

CIRCULATION OF THE ORE-PULP. 

2d—By virtue of this arrangement of circulating the 
ore-pulp through and over the heated body of mercury and 
around the amalgamating ring, it becomes possible to treat 
the thinnest ore-pulp successfully, and to save the finest 
particles of floating metal. It is principally for the reason 
that the thin watery pulp can be treated in this pan that it 
is more suitable for the continuous-pan amalgation process 
than any other pan. 

One of the main difficulties commonly encountered in the 
continuous pan process, as ordinarily used, arises from the 
fact that the ore-pulp must necessarily go to the pans as it 
comes from the stamp battery, without previous settling, 
and that the great amount of water required in crushing 
and discharging the ore from the mortars dilutes it too 
much to support the particles of mercury which must be 
scattered through it to effect the necessary contact of metal 
and mercury for the purposes of amalgation. 

If the ore-pulp is not stiff enough to support the floating 
globules of mercury, no satisfactory result can be obtained 
with the combination or standard pans. 

The difficulties arising from thin pulp are overcome by 



Cut 50. 
















72 


CIRCULAR OF MALTER, LIND & ROGERS. 


the use of the Malter pan, for the reason that its positive 
circulation brings every particle of floating metal in, through 
contact with the mercury, under the most favorable condi¬ 
tions for amalgation, no matter how thin the pulp. 

TREATMENT OF MERCURY IN THE PAN. 

3d—The use of the quicksilver bowl on the pan makes 
possible the inspection of the condition of the mercury, and 
its treatment with chemicals, at any time while the amal- 
gamation is going on, the mercury being kept in a solid 
body. Thus, if it be found that during the process of 
amalgamation the mercury has become inactive, as it often 
does, the proper re-agents may be immediately applied, and 
to restore its most favorable condition for amalgamation. 
Retaining the mercury in a body in the bottom of the pan 
makes it possible to heat it to a higher degree than could be 
done if it were scattered through the pulp; besides, it has the 
further advantage, that it decreases the loss of mercury to a 
minimum. If, in the amalgamation of gold, the mercury be 
scattered through the ore-pulp and permitted to pass with 
it from the pan to the settler, it can never be collected. 
Each particle of mercury lost, carrying with it some gold, 
results in serious loss. In the amalgamation of silver, which 
is about twenty times less valuable than its equivalent in 
gold, this loss from scattered mercury and amalgam is less 
serious, and less pains are taken with its collection. The 
ordinary settler serves the purpose of collecting the scatter¬ 
ed silver amalgam generally well enough, but with gold it 
is otherwise. In its treatment care must be taken from the 
beginning not to divide the'mercury, and if divided the 
settler is not as efficient a machine to collect it as the con¬ 
tinuous separators. 

The separators collect all the mercury at a small discharge, 
while in the settler it remains more or less scattered over 
the entire surface of its large bottom. Moreover, the pulling 
of plugs in the settlers causes great loss of mercury and 


amalgam, partly because of their collecting in the plug 
holes, but mainly because the outflow of the ore takes place 
some distance beneath the surface, and because the operator 
is apt to pull a plug too soon. 

COMPARATIVE COST OF WORKING GOLD-BEARING QUARTZ IN 
MALTER’S CONTINUOUS PAN PROCESS AND IN THE ORDI¬ 
NARY GOLD MILL WITH BATTERY AMALGAMATION. 

The cost of working gold ores by Malter’s method of pan 
amalgamation is not materially larger than the cost of work¬ 
ing them by the battery amalgamation, for the reason that 
the battery can be made to do more work per stamp by 50 
per cent if no amalgamation is to be done in the mortar. 
Thus, one of our ten-stamp continuous-pan amalgamating 
mills will work as much ore as an ordinary fifteen-stamp 

gold mill with mortar amalgamation. 

© © 

LABOR. 

The amount of labor required in either mill per ton of ore 
is the same, our continuous plant being thoroughly auto¬ 
matic. 

POWER. 

No more power is required in our continuous pan mills 
per ton of ore than in the ordinary gold mill. The pans 
running slowly require but little power, which is almost 
entirely economized in the stamp battery; fewer stamps are 
required per ton of ore worked. 

COST OF PLANT. 

As regards the comparative cost of plant of an ordinary 
battery mill and one of a continuous mill, per ton of ore to 
be worked, the difference in the power is not great, as it is 
usually believed to be. In fact, it is trifling and insignificant 
when the advantages of better work in the continuous pan 
process are taken into consideration. The thorough manner 
in which the ore is brought into contact with the mercury 
in the pan expedites the amalgamation of the precious 









CIRCULAR OF MALT 


metal, so that comparatively few pans are required. Two 
to four pans will suffice for a ten-stamp gold mill, and four 
to six for a twenty-stamp silver mill having a daily capacity 
of working from fifty to sixty tons of ore. % 

Settlers are not required for a gold mill, and may be dis¬ 
pensed with even in a silver mill. Tailing separators must 
be used in either mill. 

We claim the following advantages for Malter’s continuous 
method of pan-amalgation over any other amalgating pro¬ 
cess : 

1st—That the mercury and precious metal to be amal¬ 
gamated are brought in more thorough contact in it than in 
any other pan ; that, thereby, the time consumed in the 
process is shortened and the operation cheapened, while a 
most thorough amalgamation of the metal is effected. 

2d—That the first cost of an amalgamating mill is 
greatly decreased, for the reason that less motive power, 
fewer pans, and no settlers are required in a plant of this 
design than in that of any other construction to do a 
certain amount of work. 

3d—That the loss of mercury and amalgam is greatly 
diminished, for the reason that owing to the amalgamating 
ring it is not necessary to scatter the mercury through the 
pulp during the operation, and that less amalgam is floured 
becaused of slower motion and decreased attrition. 

4th—That the mercury can be kept in better condition to 
do its work during the process in this pan than in any other 
pan. 

5f,h—That owing to the better circulation of the ore-pulp, 
fine float gold and light chlorides are less liable to escape 
than in any other pan-process. 


., LIND & ROGERS. 


73 


THE USE OF SODIUM AMALGAM. 


To use sodium amalgam effectively is one of the most 
difficult tasks in practical metallurgy. Gold ores which are 
difficult to amalgamate may be successfully amalgamated by 
a judicious use of sodium amalgam in the mercury. Such 
ores are especially tellurides of gold or gold in alloy with 
more or less silver, rusty gold, such as occurs in decomposed 
or in roasted ores, and very fine float gold. Quicksilver will 
not readily unite with metallic silver or gold in alloy with 
equal parts of metallic silver, but if one drop of sodium 
amalgam be added to a large body of the quicksilver, the 
amalgamation will take place at once. The effect of sodium 
amalgam upon the capacity of mercury to amalgamate with 
other metals is but of short duration, and addition of too 
much sodium amalgam at a time to a body of mercury has 
rather a deleterious than a beneficial effect. Hence, 
if a good result of the use of sodium amalgam is to be ex¬ 
pected, it must be added in proper doses at short intervals to 
the mass of mercury used in the amalgamating pan. It 
cannot be very well used in an amalgamating pan in which 
the mercury is scattered through the pulp during the process 
of amalgamation; but it can be easily used in the Malter pan 
by applying it to the mercury in the bowl in drops every few 
minutes. 

Mr. Guido Kustel constructed an apparatus for the feeding 
of sodium amalgam into the mercury. It consists of a 
hermetically closed vessel of iron, at the lowest point of 
which there is a small outlet, which is opened at short 
intervals to permit a few drops to pass out. 

We are prepared to furnish this apparatus. 








74 


CIRCULAR OF MALTER, LIND & ROGERS. 


COATING OF COPPER PLATES. 


The coating of copper plates or pan-rings with mercury 
for the purpose of amalgamation, may be greatly facilitated 
by first dissolving the mercury in pure nitric acid. The 
snow-like mass nitrate of mercury, which results, is then 
rubbed by means of a cloth, or otherwise, over the copper; a 
coating of metallic mercury immediately results. Plates to 
be coated should be first thoroughly cleaned and scoured by 
rubbing with a piece of brick or soft stone, and then washed 
with a thin solution of cyanide of potassium. 

GRINDING OF ORES. 


The stamp, ordinarily, is the most effective means for the 
reduction of brittle ores to a certain degree of fineness. Some 
ores, however, are not easily pulverized by the stamp to the 
fineness required for the extraction of the metal. Soft and 
clayev ore, for instance, may often be ground to better 
advantage. The amalgamating pan is not an efficient 
grinder, the ore does not readily go between the muller anjl 
the dies, and the same used as an amalgamator as well as a 
grinder will inevitably destroy part of the amalgam by 
flouring. 

For the purpose of grinding ores and preparing them for 
subsequent amalgamation we use a patent iron arastra, of 
which the accompanying cut gives an illustration. 

The arastra is constructed in form of a pan with vertical 
side, to the inner periphery of which is secured a ring or die, 
which is best made of the tires of locomotive driving-wheels. 

A muller plate carries the grinding blocks, which lie 
loosely upon it, being held in place by diaphrams cast on 
the muller. As the muller revolves the grinding blocks, 
they are pressed out by the centrifrugal force against the 
ring or die, thereby crushing the ore which falls continuously 
1) 'tween them as it is charged into the arastra from above. 



An inverted hopper serves to distribute the ore between 
the shoes and dies. 

Water is introduced beneath the muller plate, and in its 
upward flow carries the ore with it to the discharge opening, 
which is placed near the upper edge of the sides of the 
arastra. The grinding block may be made of either iron or 

O O y_ 

stone. 






































































































CIRCULAR OF MALTER, LIND & ROGERS 


75 



Cut 53—Front Elevation of Girard Mill at Tombstone, A. T. 

































































































































































































































































76 


CIRCULAR OF MAL 
CHLORINATION PROCESS. 


The gold-bearing sulphurets, obtained by concentration 
from the tailing of gold mills, resist amalgamation, and are 
usually treated by the chlorination process. 

This process consists of four distinct manipulations. 

1st—Roasting of the sulphurets. 

2d—Chlorinating the gold. 

© © # # 

3d—Leaching the soluble chlorine of gold out of the in- 
© © 

soluble mineral. 

4th—Precipitation and melting. 

ROASTING. 

The roasting required by the gold-bearing sulphurets, 
which are to be treated by the chlorination process, must be 
a dead roasting, i.e., all the sulphurets and sulphates must 
be thoroughly oxidized. 

If sulphates of iron remain in the roasted ore, they would 
precipitate the chlorinated gold in the leaching vat and 
make its extraction impossible. If sulphates of copper 
remain in the roasted ore, they might re-act upon the oxides 
of iron, converting them into sulphates, and cause them the 
same trouble. 

The furnace best suited for the purpose of dead roasting 
of gold-bearing sulphurets is the reverberatory furnace. If 
the chlorination works may be conveniently located on the 
side of the hill, this furnace is best made in steps, that is 
the hearth is made in two, three or more compartments, of 
which the first, the one upon which the ore is charged, is the 
highest; and the last, the one near the fire-place where the 
roasted ore is discharged, is the lowest. 

The ore is raked by hand continually to move it forward 
to the fire and to expose every particle of it to the oxidiz¬ 
ing influence of the flame, and thus hasten the process of 

roasting. 

© 


LIND A ROGERS. 


The heat must be applied gradually to prevent the sulphur 
from igniting too suddenly, which would cause lumping of 
the ore ; should it occur, then the lumps must be sifted from 
the finer ore to be re-crushed before leaching. 

Especial care must be taken to keep the temperature in 
the furnace low if galena be present in the ores, and the 
stirring must be continuous to prevent the fusing of sul- 
phides and matting. 

If magnesia and lime are present in the ore it is not well 
suited for the chlorination process, for the reason that these 
minerals absorb the chlorine gas, and thereby vastly increase 
the expense of the process. Mr. G. F. Deetken claims to 
have remedied this difficulty by the addition of salt to the 
roasting ore shortly before its discharge from the furnace. 

To ascertain whether the base metals in the ore are 
thoroughly oxodized, and the roasting operation finished, a 
sample of the ore may be taken from the furnace and put 
into a glass of water, then a few drops of the solution of 
ferrocyanide of potassium are added ; if the water turn 
bluish or reddish or greenish the roasting must be continued 
until no such reaction takes place. Mechanical furnaces, 
such as the Bruckner, may be used, they have the advan¬ 
tage of economizing the labor of raking and stirring the ore, 
but they do not cheapen the process, for the reason that much 
power is consumed during the long time necessary to effect 
a dead roasting; beside more loss is occasioned in them by 
dusting than in the reverberatory. 

The roasted ore is drawn from the furnace, spread on a 
cooling floor, and after awhile moistened either by hand or 
with a sprinkling apparatus. 

CHLORINATION OF THE GOLD. 

The moistened ore is treated with chlorine gas, and for 
that purpose is shoveled or dumped and sifted into wooden 
vats with low sides, the insides of which are coated thickly 
with asphaltum or tar and pitch. These vats have false 






CIRCULAR OF MALTER, LTND & ROGERS. 


77 


bottoms of perforated wood, over which filters of coarse 
quartz and fine sands are placed in layers, the coarser quartz 
down, the finer sands on top. 

The chlorine gas is introduced through a lead pipe open¬ 
ing near the bottom of the vat ; it rises through the ore, 
and when it begins to show itself upon the surface the vat 
is covered with a wooden cover, which is made tight by 
luting it around the edges with a proper kind of clay, which 
will not crack when drying. The ore is left under the 
influence of the chlorine gas for from 24 to 48 hours, until 
all the gold in it has been converted into soluble chlorides. 
The chlorine gas is.generated in a leaden vessel, from proper 
proportions of common salt, peroxide of maganese, sulphuric 
acid and water, which are subjected to a slight heat. 

The gas is purified before its admission to the ore tanks 
by passing it through water, which frees it from muriatic 
acid and other impurities. 

LIXIVIATION. 

When the ore is thoroughly chlorinated, the cover is 
removed from the vat and water is run over the surface of 
the ore continuously. Seeping through the ore it passes to 
the bottom of the vat and out through a pipe which conducts 
it to another vat, the precipitation vat. This flow of water 
leaches the soluble chlorine of gold from the ore. To ascer¬ 
tain when the operation of leaching is finished, a sample of 
the leaching water is taken from time to time and sulphate 
of iron added to it. If chlorine of gold be still present in 
the solution, a dark bluish precipitate will result. The 
leaching with water must be continued until no precipitation 
in the sample takes place by the addition of the sulphates of 
iron. 

PRECIPITATION AND MELTING 

A solution of sulphate of iron is used to precipitate the 
chlorine of gold from the liquor in the precipation vat. 


After adding this precipitant the liquor is stirred and then 
allowed to subside until the surface becomes clear. Then a 
sample of this clear liquor is taken and sulphate of iron 
added to it to ascertain whether all the gold has been pre¬ 
cipitated from the solution. If the sample shows strong 
discoloration or some precipitation, more sulphate of iron 
must be added to the solution in the precipitating tank. 

In order to ascertain whether a sufficient amount of sul¬ 
phate of iron has been added to the liquor in the precipitation 
tank, a tumblerful of the clear liquor may be taken from 
the top of the vat, and if to it is added a little of the solution 
known to contain chlorine of gold, a precipitation of the 
gold must take place; if it does not take place, then more 
sulphate of iron must be added to the liquor in the precipita¬ 
tion vat. 

After these tests show a complete precipitation of the 
gold, and the precipitate has settled to the bottom of the vat, 
which may require from one to two days, then the clear 
liquor is drawn off, the gold collected, filtered, and washed 
with dilutions of muriatic acid and warm water until all 
acidity is removed, when the gold is dried and melted in 
crucibles with borax. The base metal in it can be gotten 
rid of by the addition of nitric acid and skimming of the 
molten gold. 





78 


CIRCULAR OF MALTER, LIND & ROGERS. 



CHLORINATION WORKS. 


The above illustration shows the elevation of chlorination 
works, having a daily capacity of working 5,000 pounds of 
sulphurets. 

The ores are first crushed by stamps, and then concen¬ 
trated to separate the worthless gangue from the metals in 
order to prevent the too great absorption of chlorine gas, 


which would largely increase the cost of the operation and 
might defeat the object of reduction by this process. The 
crushing and concentrating machinery is not shown in the 
above cut. After crushing ami concentrating, the ores are 
dried by heat and brought in cars to the upper floor of a long- 
reverberatory furnace, havingthreesteps or floors, on different 
levels, as shown in the cut. In this furnace the ore is sub¬ 
jected to a careful dead roasting, under the influence of a 
gradually increasing heat. 



















































































































































































































CIRCULAR OF MALTER, LIND & ROGERS. 


79 



Cut 55—Ground Plan of Chlorination Works. 


The upper floor, where the ore is introduced, being the 
farthest from the fire-place and the lower floor, where it 
is discharged, being nearest the fire. The ore is continually 
raked by hand, and gradually moved toward the fire. A 
sprinkling apparatus is placed between the furnaces and the 
leading tanks. The chlorine gas is generated in four leaden 
tanks or vessels, shown in the middle of the cut, by the 
decomposition of oxide of manganese salt and sulphuric 
acid. 


The gas is purified before its admission to the ore tanks, 
by passing through water, which frees it from muriatic acid 
and other impurities. The chlorination of the gold takes 
place in eight large vats or ore-tanks, placed on the second 
floor of the works, four on either side. The chlorinated gold 
is drained from these vats into the precipitation tubs placed 
beneath and immediately in front of them. The gold is pre¬ 
cipitated by sulphurets of iron from its solution and dried 
and melted. 




























































































































































































































































































80 


CIRCULAR OF MALTER, LIND & ROGERS. 


LIXIVIATION PROCESS FOR GOLD AND SILVER. 


Gold-bearing sulphurets or ores, in which the gold is con¬ 
tained in coarse grains, cannot be worked by the chlorination 
process. Chlorine gas will not readily dissolve coarse gold. 

If the gold ores contain much silver, it is a matter of great 
difficulty to extract the precious metals from them by the 
chlorination process. If silver very largely predominates, 
then the chloridization of the metal by means of roasting 
with salt, and subsequent amalgamation, will probably give 
better results. ~ If silver does not predominate too largely or 
the ores are to be leached anyway, for the reason that amal¬ 
gamation be not feasible, then two courses may be pursued: 

1st—Salt may be added during the roasting process for 
the purpose of chloridizing the silver; then the roasted ore 
may be chlorinated to put the gold in soluble condition, 
when it may be extracted by water, and can then be leached 
out with hyposulphide of soda. 

The silver solution is collected in separate vats and pre¬ 
cipitated by the addition of sulphide of calcium, as sulphide 
of silver in the manner described in the leaching process for 
silver. The silver precipitates settle more readily than 
those of gold. It is filtered, washed with hot water, dried 
and roasted in a furnace with slowly increasing heat to drive 
off part of the sulphur. Then it is melted with borax and 
iron scraps in a black crucible, the matt and slag are 
skimmed off and the metal is poured. 

This method has been repeatedly tried by metallurgists, 
but satisfactory results have not usually been obtained. 

2d—The ore may be roasted without salt until all the 
. base metals are oxidized, then it may be chlorinated and the 
gold leached out. The silver remains in the ore; it is dried, 
sulphur and salt are added, and the ore is subjected to a 
chloridizing roasting, which can be easily effected with little 
expense in a mechanical furnace. 


After the silver is thus chloridized, it may be readily ex¬ 
tracted by leaching or by amalgamation. 


Challenge ore feeder 


WEIGHTS OF MACHINERY USED IN QUARTZ MILLS 

Grizzley or ore screens.650 to 800 lbs. 

Blake crusher, 9x15.... 5,400 “ 12,000 “ 

“ “ 8x10 ...4,100 “ 7,000 “ 

Standard crusher, 8x10.... 4,000 “ 8,000 “ 

9x15_4,800 “ 10,000 “ 

. 750 “ 

Roller “ “ 650 “ 

Stanford “ “ 600 “ 

Mortars for five 850-lb. stamps. . . . 5,200 “ 

Stamp dies “ “ “ .... 110 “ 

“ shoes “ “ “ .... 120 “ 

“ stems “ “ “ _ 335 “ 

“ heads “ “ “ .... 225 “ 

“ tappets “ “ “ 150 to 200 “ 

cams, double arms. .. 175 to 250 “ 

cam shaft 5| diam.xl4| long 1,160 “ 

Frue & Triumph concentrators 2,280 
Grinding and amalgamating pans, 3,800 to 6,500 lbs. 

Settlers. 2.400 to 5,500 “ 

Clean-up pans. 600 to 1,300 “ 

Retorts. 1,000 to 2,600 “ 

Approximate shipping weight of ten-stamp gold mill, 
using Knight or Felton water-wheel and two belt concentra¬ 
tors—28 tons. 

Approximate shipping weight of twenty-stamp gold mill, 
having eight belt concentrators, with hurdy-gurdy water¬ 
wheel for power—59 tons. 

Shipping weight of machinery for ten stamp wet-crushing 
silver mill, using four pans and two settlers, clean-up pan, 
etc.—45 tons. Engine, boiler, etc.—70 tons. 



















CIRCULAR OF MALTER, LIND & ROGERS. 


81 


Shipping weight of machinery for 10-stamp dry-crushing 
mill, 82 tons. 

Power required to operate a 20-stamp wet-crushing silver 


mill (850-lb. stamp): 

20 stamps @ h. p. per head. 30 

12 grinding pans @ 5 h. p. 60 

6 settlers @ 3 h. p. 18 

1 9x15 crusher. 6 


Total h. p.114 


Gold mills require from 1| to 2 h. p. per stamp, and from 
5 to 8 h. p. for rock-breakers. Belt concentrators require 
from f to 14 h. p. for each machine. 

Power for 10-stamp dry-crushing mill (850-lb. stamp) : 


10 stamps @ 1£ h. p. per stamp. 15 

4 pans @ 3 h. p. 12 

2 settlers @ 2 h. p. 4 

1 48” revolving furnace. 2£ 

1 8x10 crusher. 5 

1 dryer... 5 

Total h. p. 44£ 


Water required for stamp mill per hour in gallons : 

GALS. 

Boiler for each h. p. per hour. 74 


Stamps “ “ “ “ 32 

Pans “ “ “ “ 120 

Settlers “ “ “ “ 60 


Water required for stamp mills per minute in gallons : 

GALS. 

For 20-stamp wet-crushing mill. 65 

“ 10 “ “ “ “ . 32 

“ 10 “ dry “ “ . 15 

Water required for 20-stamp wet-crushing silver mill in 
pounds: : 

120 h. p. boiler, 20 stamps, 10 pans, 5 settlers and clean¬ 
up pan requires 568 lbs. of water per minute. 

Water required for 10-stamp wet-crushing silver mill 
per minute, 265 lbs. 

Water required for a 10-stamp dry-crushing mill 120 lbs. 
per minute. 




























Cut 56—Small Pumping- Engine and. Pumps, for moderate depth of shaft. 


82 


CIRCULAR OF MALTER, LIND & ROGERS. 































































































































































































































































































































































































































































CIRCULAR OF MALTER, LIND & ROGERS. 


83 



V _*i IV JI T- 1 - '- - > J 

Side Elevation. End Elevation. 

Cut 57—Hoisting Works, with Direct-acting Engines with Barclay’s Cut-off, at St. Helena Mine, Mexico, 

built by Malter, Lind & Rogers. 











































































































































































































































































































































































































84 


CIRCULAR OF MALTER, LIND & ROGERS. 


Hoisting Machinery, Etc. 


In this department we are prepared to furnish and erect 
Hoisting Works for shafts of any depth, provided with 
every modern improvement for hoisting cages and cars 
with convenience, safety and dispatch. 

For deep mines the direct-acting engines are to be pre¬ 
ferred, but for shafts ranging from 100 to 800 feet in 
depth the geared hoists are more generally used. We build 
the latter with single or double reels, for either round or 
flat rope, having either single or double gears of the 
friction, spur and curved-tooth patterns. These engines 
are provided with reversible links, and the reels are 
controlled by powerful hand and foot brakes. 

The direct-acting engines are all highly finished, and 
usually provided with the Barclay cut-off, which is simple in 
construction, easy to set and manage, and very effective in 


saving fuel, giving general satisfaction in use. 

We also provide Hoisting Works to be run by water 
power, using the turbine water-wheels where low heads are 
only available, and the Knight, Pelton or hurdy-gurdy 
wheels where high heads can be secured, arranged with 
suitable gates controlled by governors of the most improved 
construction; the power is transmitted by either belts or 
ropes from horizontal shafts, so that no gearing is required. 

We furnish improved Safety Cages, Mining Cars, Skips, 
Water and Ore Buckets, and all other appliances for use in 
and about mines. 

We provide and erect wire-rope tramways, with every 
convenience for conveying ores cheaply and in large 
quantities from the mine to the mill. 









CIRCULAR OF 


MEASUREMENT OF LAND. 

16| feet. 1 rod 

66 feet.1 chain 

5280 feet. 1 mile 

43,560 square feet. 1 acre 

A square the length of one side of which is 

208 feet 84 inches, contains. 1 acre 

295 “ If “ - 2 “ 

361 “ 6 ■ “ “ 3 “ 

466 " 8| “ “ 5 “ 

660 “ “ . 10 “ 

933 “ 4£ “ “ 20 “ 

1320 “ “ 40 “ 

1866 “9^ “ “ . 80 “ 

2640 “ ‘ “ 160 “ 

5280 “ “ 640 *• 

Millsites usually contain live acres. 


EIGHTS AND MEASURES OF QUARTZ, SAND, ETC. 
13 cubic feet of quartz in lode.1 ton 


20 

(t (< cc 

cc 

broken . 

1 

cc 

25 

i< cc .< 

cc 

sand. 

1 

cc 

18 

n ci n 

cc 

earth . 

1 

cc 

17 

Cl cc Cl 

cc 

day. 

1 

cc 

18 

cc cc cc 

gravel before digging, 

1 

cc 

27 

cc cc cc 

cc 

after 

1 

cc 


WEIGHTS OF METALS. 



For cast iron, mult, cubic in. x .26 =lbs. 

avoir, 

cc 

zinc, 

cc 

“ x .253= “ 

CC 


cc 

tin, 

cc 

“ x .263= “ 

cc 


cc 

steel, 

cc 

“ x .282= “ 

Cl 


(C 

brass, 

cc 

“ x .3 = “ 

cc 


a 

copper, 

cc 

“ x .32 = “ 

cc 


cc 

lead, 

cc 

“ x .41 = “ 

cc 



MALTER, LINI) & ROGERS. 


85 



CAPACITIES OF ROUND 

TANKS. 

Height. 

Diameter. 

Gallons. 

6 . 

. 8*. 

. 2,000 

7. 

. 9 5-12... 

. 3,000 

7. 

. 11 . 

. 4,000 

7. 

. 11 5-6. . . . 

. 5,000 

7. 

. 134. 

. 6,000 

7. 

. 14 . 

. 7,000 

8. 

. 14 . 

. 8,000 

8. 

. 15 . 

. 9,000 

8. 

. 16 . 

. 10,000 

12 . 

. 16 . 

. 15,000 

12 . 

. 184. 

. 20,000 


USEFUL DATA. 


One miner’s inch equals the quantity of water which will 
flow through an opening one inch square under a pressure 
or head of four inches—being about 107 lbs. per minute. 

1 cubic foot of water weighs 62.3 lbs. (U. S. Standard). 

1 cubic foot of water contains 7.48 gallons. 

1 pound avoirdupois equals 16 ounces or 7,000 grains. 

1 pound troy equals 12 ounces, or 5,760 grains. 

1 gallon contains 231 cubic inches. 

1 gallon of water weighs 8.33 lbs. 

1 vara equals 2.75 linear feet. 

1 league equals 13,750 feet or 2.6 miles. 

1 square (roofing or flooring) equals 100 square feet. 

1 long ton equals 2,240 pounds. 

1 short ton as commonly used equals 2,000 pounds. 

1 span equals 9 inches. 

1 fathom equals 6 feet. 

1 cable length equals 120 fathoms. 

1 foot pound equals work required to raise one pound 
vertically one foot. 
















































86 


CIRCULAR OF MALTER. LIND & ROGERS. 


TATUM & BOWEN 


34 and 36 Fremont Street 91 and 93 Front Street 

SAN FRANCISCO PORTLAND, OR. 

-MANUFACTURERS OF- 


MINING AND SAWMILL MACHINERY 


ENGINES, ETC. 

-DEALERS IN- 

Engines, Boilers, Wood and Iron=working Machinery, 

Steam Pumps, Hoisting Engines 
MILL AND MINE SUPPLIES 


-.SOLE AGENTS- 

Albany Lubricating Compound, Cylinder and Lubricating Oils 
Shultz Patent Enlled Leather Belting and Lace Leather, 

Hoe ChiseLTooth Saws, Gardner Governors 

Economic boilers, Etc. 












CIRCULAR OF MALTER, LIND & ROGERS. 


State Assay Office 


FALKENAU & REESE 

ASSAYERS 

ANALYTICAL, TECHNICAL AND CONSULTING CHEMISTS 

ROOM 16 SAFE DEPOSIT BUILDING 
COR. MONTGOMERY AND CALIFORNIA STS., - - SAN FRANCISCO 


Special attention given to receiving consignments of Ores and Base Bullion, attend¬ 
ing to the Sampling, Assaying and Negotiating for their Sale. 

ANALYSIS OF ORES, Mineral and Drinking Waters, Soils, Commercial Articles, 
etc. Investigations for Poison, Inspection of Mines, Mineral Springs, Metallurgical and 
Manufacturing Establishments promptly attended to. 

Instructions given in Assaying and all branches of Chemistry. 














Special Notice. 


Contracts made to furnish and erect stamp mills for the reduction of all 
classes of gold and silver ores. 

Concentration plants of the most improved construction, Smelting and Leach¬ 
ing works for silver, copper and lead ores. 

Hoisting and Pumping Works for shafts of any depth. We also furnish 
patent steel Cornish Rolls, Rock-breakers, for coarse or fine crushing, Sizing 
Screens and Jigs of one, two, three, and four compartments, double or single 
Charge and Continuous-working Roasting Furnaces, Stamp Batteries for wet or 
dry crushing, Grinding Mills, patent Hydraulic Separators and Concentrators, 
Improved Corliss, Meyer’s cut-off, High-speed and Plain Slide-valve Engines, 
Horizontal and Vertical Tubular Boilers, Amalgamating Pans for gold or silver 
ores, Settlers. Retorts, Shoes and Dies, (steel or iron) Cams, Tappets, and general 
mining and milling supplies of all descriptions. 

Working tests made of ores to ascertain the best method of reduction. 



Jipa 

wm. 

^im\m 

Jaikdici 


GTI^W.fpJ 

DiM§Jl±0 

Sllfe 

cn^fpj 

EJJ'/fgjj'Uf! 

sms. 

3£j 

H 


* 

SlltlS 


Gmlna 

rtmnz 

Cil^fFl 

SJMlki 

Cnl.w.fTa 

WjjMn 

» 

^PP 

SlMfS 

Sl£ 

.7TF7 r ^ -= -= - - -. • - • - . 'il ■~ ^ 3== ~ ^ v —CT. . -7 ■■■■--—: ^= - -.-.-= --.-=r~ --■:^-^i~=^:-.^.^=-------=£- T . ==.--- 
















































































































































































































































































































